| Understudy | Part | Currently on notice for | Support Person | Items | Original Cast | Clash |
| Abigail Cunneen | Earth Bridge 2 | | TBC | 1.6 | Eliza Herold | |
| Ada Princep | Tommy | | TBC | 6.3, 6.4, 6.5 | Nick Anderson | |
| Ada Princep | Rory | | TBC | 1.3, 1.5 | Spock Po | |
| Adele McIntosh | Simon | Dress Rehearsal 2 | TBC | 1.5, 1.7, 3.5 | Leo Van De Camp | |
| Adele McIntosh | Scared Villager Post Chorus | | TBC | 4.3 | Georgia Cohalan | ⚠️ 4.3 |
| Alex Bates | Wilson | | TBC | 1.7 | Cooper Gregory | |
| Alex Haviland | Blimp Jenny | | TBC | 1.5, 3.1, 3.5 | Rosie Briffa | |
| Alex Lau | Contestant 2 | | TBC | 5.4 | Will Issell | |
| Alex Crawford-Paton | Happy B2 | | TBC | 5.1 | Sylvie Gibbons | |
| Alexander Cleary | Happy V3 | | TBC | 5.1 | Claire Haggart | |
| Alexander Cleary | Sixty V4 | | TBC | 1.1 | Priscilla Qiu | |
| Alicia Po | Chad | | TBC | 4.1 | Liam Gregory | |
| Amber Summerbell | S.A.D. V2 | | TBC | 4.3 | Izzie Baker-Mayer | ⚠️ 4.3 |
| Amelia McIntosh | Tim | Performance 4, Performance 5 | TBC | 1.5, 2.6, 6.1, 6.3, 6.7, 7.1, 7.2 | Lee Della-Rossa | ⚠️ 2.7 |
| Amelia McIntosh | Never V3 | Performance 1 | TBC | 6.2 | Abigail Cunneen | |
| Amy Lim-Joon | Back Post 1 | | TBC | 5.6 | Oscar Georgiou | |
| Amy Lim-Joon | Hayley | | TBC | 1.5, 3.5 | Sarah Duthie | |
| Angie Malcontenti-Wilson | Joy | | TBC | 1.2, 2.1, 2.5, 3.2, 4.2, 5.2, 7.3 | Alex Taylor | ⚠️ 2.2 |
| Angie Malcontenti-Wilson | S.A.D. Extras | | TBC | 5.2 | Benj Pritchard, Kieran Talbot | |
| Archer Bastin | Neville | | TBC | 1.3, 2.1, 2.5, 4.2, 5.2, 7.3 | Liam Rafferty | |
| Ari Coram | Sammy | | TBC | 1.4, 1.5, 3.5 | Christina Chernt | |
| Aria Dang | Never PC2 | | TBC | 6.2 | Fiona MacKay | |
| Aria Dang | Sky V4 | | TBC | 3.6 | Leo Connellan | |
| Ava Rose Argent | Stop 2.2 | | TBC | 6.6 | Julian Renteria Vergara | |
| Aydin Karabardak | Cam | | TBC | 4.2 | Ben Tierney | ⚠️ 4.3 |
| Ben Tierney | Funk Bridge 2 | | TBC | 2.7 | Rose Brown | |
| Ben Tierney | Sixty V3 | Dress Rehearsal 1, Dress Rehearsal 4, Performance 1 | TBC | 1.1 | Adele McIntosh | |
| Benj Pritchard | One V3 | | TBC | 3.3 | Evie Lewis | |
| Benjamin Georgiou | Happy V2 | | TBC | 5.1 | Evan Quilty | |
| Bowie Dekok | Businessman | Performance 2, Performance 5 | TBC | 1.4, 1.5, 3.5 | Liam Royston | |
| Brendan Black | Heather | | TBC | 2.6 | Sylvie Kahler | |
| Brendan Black | Captain | | TBC | 1.4, 1.5, 3.5 | Jude Lange | |
| Brittany Tiernan | Conductor | | TBC | 6.3, 6.4, 6.5, 7.1 | Elaine King | |
| Caitlin Haines | Announcer | Performance 1 | TBC | 2.5, 5.4 | William Conn | |
| Caitlin Haines | Tour Guide Bob | | TBC | 1.4, 1.5, 3.5 | Nicholas Fear | |
| Carla Royston | Dad | Performance 2, Performance 4 | TBC | 4.1 | Brendan Black | |
| Charlie Fraumano-Braddy | Grunge V3 | | TBC | 2.2, 2.4 | Oliver Wales | |
| Chloe Anderton | Earth V2.1 | | TBC | 1.6 | Marc Phillips | |
| Christina Chernt | Brett | | TBC | 6.4, 6.5 | Harry Lewis | |
| Claire Haggart | Back V1 | Dress Rehearsal 4 | TBC | 5.6 | Sam Leslie-Hughes | |
| Claire Haggart | Sixty V1 | | TBC | 1.1 | Archer Bastin | |
| Claudia Wright | Earth V1.1 | Performance 1 | TBC | 1.6 | Scarlett Forbes | |
| Coco Lewis | Young Rap G | | TBC | 6.1, 6.3, 6.5, 6.6, 7.1 | Emma Haggart | ⚠️ 6.6 |
| Cooper Gregory | Gladys | | TBC | 4.1 | Remy Havas | |
| Cooper Gregory | Swami | Dress Rehearsal 1, Dress Rehearsal 3, Dress Rehearsal 4 | TBC | 3.4 | David Coleman | |
| David Coleman | Mani | | TBC | 2.5 | Edwin Thomas | |
| Edwin Thomas | Earth V2.2 | | TBC | 1.6 | Evelyn Read | |
| Elaine King | Rap Grandma | | TBC | 5.5, 5.6, 5.7, 6.1, 6.3, 6.6, 6.7, 7.1, 7.2 | Evie Gionfriddo | ⚠️ 6.3, 7.1 |
| Eleanor Walker | Head Glad | Performance 2, Performance 3, Performance 4 | TBC | 4.1 | Luke Chandler | |
| Eleanor De Vere Gould | One V2 | Dress Rehearsal 4 | TBC | 3.3 | Harry Lawson, Harriet Bunting | |
| Eliza Lane | Ty | | TBC | 1.5, 1.7 | Robbie Haviland | |
| Eliza Herold | Headmaster | | TBC | 1.1 | Will Issell | |
| Ellie Brown | Patrice | | TBC | 5.3, 5.5, 5.6, 5.7 | Alex Bates | |
| Ellie Richmond | Cyril | | TBC | 1.2, 4.2 | Estelle Tillott | ⚠️ 4.3 |
| Elliot Thomas | Brodie | Dress Rehearsal 1, Performance 4 | TBC | 1.4, 1.5, 2.1, 2.2, 2.3, 2.4, 3.1, 3.5 | Emil Russell | |
| Eloise Witham | Ashley | | TBC | 1.3, 1.5 | Grace O'Connor | |
| Elsa Stanaway | Blaire | | TBC | 1.5, 3.5 | Harper Connellan | |
| Elsa Stanaway | Millie | | TBC | 1.5, 3.1, 3.5 | Maddie Burns | |
| Emil Russell | Never V1 | | TBC | 6.2 | Ava Rose Argent | |
| Estelle Tillott | Cassy | | TBC | 3.5 | Khooshi Khadria | |
| Evan Quilty | Patty | | TBC | 5.3 | Oscar Balfe | |
| Evelyn Read | Funk Bridge 1 | | TBC | 2.7 | Tyler Mason | |
| Evelyn Read | Sixty PC2 | | TBC | 1.1 | Caitlin Haines | |
| Evie Lewis | Hoody | | TBC | 7.1 | Stephanie Millicer | |
| Felix Carrillo | Ari | | TBC | 6.4, 6.5 | Xander Borchard | |
| Flynn Helmer | Leo | | TBC | 1.5, 1.7, 3.5 | Jack Phillips | |
| Frankie Wines | Hoodlem | | TBC | 7.1 | Nicky Brelaz | |
| Fraser Sue | Blake | | TBC | 1.4, 1.5, 2.1, 2.2, 2.3, 2.4, 3.1, 3.5 | Ryker Hopgood | ⚠️ 2.2, 2.4 |
| Fraser Sue | Earth V3.2 | | TBC | 1.6 | Sophie Zhao | |
| Georgia Cohalan | Back PC 2 | | TBC | 5.6 | Alexander Cleary | |
| Georgia Cohalan | Sixty PC1 | | TBC | 1.1 | Xavier Jenkin | |
| Grace O'Connor | Jimmy | | TBC | 2.1, 2.3, 2.4, 3.5 | Harvey Keecha | |
| Harper Connellan | Kelsi | Dress Rehearsal 1, Dress Rehearsal 2 | TBC | 6.4, 6.5 | Claudia Wright | |
| Harriet Bunting | Bryson | | TBC | 1.4, 1.5, 3.5 | Aydin Karabardak | |
| Harry Lawson | Boone | | TBC | 3.5 | Rupert Thomas | |
| Henry Conn | Sri | | TBC | 3.4 | Eliza Lane | |
| Hunter Johnson | Never PC1 | | TBC | 6.2 | Spock Po | |
| Isabella Cobby | Dazza | Performance 3 | TBC | 5.2 | Flynn Helmer | |
| Izzie Baker-Mayer | Sam | | TBC | 2.5, 7.2 | Mio Stokkeland | |
| Izzie Baker-Mayer | Zen | | TBC | 2.5 | Linus Desmons | |
| Jack Phillips | Cyrilla | | TBC | 1.2, 4.2 | Tammy Bishop | ⚠️ 4.3 |
| James Talbot | Temp Rap G | | TBC | 6.1 | Ada Princep | |
| Jess Manns | Earth V3.1 | | TBC | 1.6 | Eleanor De Vere Gould | |
| Jim Swan | Grunge V1 | | TBC | 2.2, 2.4 | Henry Conn | |
| Jordan Gong | Back V3 | | TBC | 5.6 | Kayla Karabardak | |
| Jordan Gong | Town V4 | | TBC | 4.3 | Grace Jenkin | ⚠️ 4.3 |
| Joshua Marot | Brad | | TBC | 4.1 | Alex Haviland | |
| Jude Lange | Sven | | TBC | 5.5, 7.2 | Evelyn Cobby | |
| Julia Hannink | Judge Cate | | TBC | 4.2 | Otto Petroro | ⚠️ 4.3 |
| Julia Hannink | Vernon | | TBC | 6.4, 6.5 | Harry Lawson | |
| Julian Wu | Benson | | TBC | 1.5, 3.5 | Alex Lau | |
| Kayla Karabardak | Carlos | | TBC | 1.3, 1.5 | Benjamin Georgiou | |
| Khooshi Khadria | Earth V1.2 | | TBC | 1.6 | Lucy Lin | |
| Kieran Talbot | Barry | | TBC | 1.5, 2.5, 3.5 | Joshua Marot | |
| Kieran Jellema | Jenny | | TBC | 6.3, 6.4, 6.5 | Leah Maffett | |
| Kieran Talbot | Tour Guide Judy | | TBC | 1.4, 1.5, 3.5 | Ellie Richmond | |
| Leah Maffett | Fleur | | TBC | 3.5 | Victoria Jiang | |
| Lee Tsourvakas | Funk V1 | | TBC | 2.7 | Maddie Parker | |
| Lee Tsourvakas | Town V5 | | TBC | 4.3 | Zara Summerbell | ⚠️ 4.3 |
| Leo Van De Camp | Cody | | TBC | 4.2 | Charlie Fraumano-Braddy | ⚠️ 4.3 |
| Leo Connellan | Gabriella | | TBC | 6.4, 6.5 | Ellie Brown | |
| Liam Kelly | Riley | | TBC | 2.1, 2.3, 2.4, 5.5, 5.6, 5.7, 7.2 | Coco Lewis | |
| Liam Royston | Thumbs | Dress Rehearsal 1 | TBC | 2.6, 5.5, 5.6, 5.7, 6.1, 6.3, 6.7, 7.1 | Elliot Thomas | ⚠️ 2.7 |
| Liam Gregory | Bede | | TBC | 1.5, 3.5 | Mia Porteous | |
| Lilly Scott | Hood Iss | | TBC | 7.1 | Lee Tsourvakas | |
| Lily McLachlan | Contestant 1 | | TBC | 5.4 | Niamh Reid | |
| Lincoln Teng | Radio | | TBC | 6.1 | Kieran Jellema | |
| Linus Desmons | Mildred | Performance 3 | TBC | 6.4, 6.5 | Liya Ilsley | |
| Linus Desmons | Sign Kid | | TBC | 1.4 | Olivia Wise | |
| Liya Ilsley | Farmer John | | TBC | 1.5 | Sihas De Silva | |
| Lizzy Pritchard | Reception | | TBC | 5.2 | Aria Dang | |
| Lucy Lin | Funk V3 | | TBC | 2.7 | Mia Humphries | |
| Luke Chandler | Fender | | TBC | 2.1, 2.3, 2.4, 3.5 | Carla Royston | |
| Maddie Burns | Happy V1 | | TBC | 5.1 | Rosie Briffa | |
| Maddie Parker | Morgan | | TBC | 1.3, 1.5 | Evelyn Cobby | |
| Matilda da Silva | Rooster | Dress Rehearsal 3, Performance 2, Performance 3, Performance 4, Performance 5, Performance 6 | TBC | 6.1, 7.3 | Brittany Tiernan | ⚠️ 6.2 |
| Maya Henry | Fredrick | | TBC | 6.3, 7.1 | Ari Coram | |
| Maya Henry | S.A.D. V1 | Dress Rehearsal 3 | TBC | 4.3 | Lizzy Pritchard | |
| Mia Porteous | Hood Unnit | | TBC | 7.1 | Angie Malcontenti-Wilson | |
| Mia Humphries | One V4 | Dress Rehearsal 1 | TBC | 3.3 | Ryan Cheung | |
| Milly Waldie | Jamie | | TBC | 1.2, 1.3, 1.5, 3.5, 7.2 | Tom Treasure | |
| Mio Stokkeland | Chorus Solo | | TBC | 3.6 | Mia Humphries | |
| Mio Stokkeland | Sky V1 | | TBC | 3.6 | Amber Summerbell | |
| Moose Snashall | Charlie | Dress Rehearsal 2 | TBC | 3.2, 3.4, 4.2, 5.3, 7.2 | Erin Harewood | ⚠️ 4.3 |
| Nicholas Fear | Mel | Dress Rehearsal 3 | TBC | 5.2, 5.4 | Rebecca Burns | |
| Nick Anderson | Contestant 4 | | TBC | 5.4 | Jordan Gong | |
| Nick Anderson | Theo | | TBC | 1.5, 3.1, 3.5 | Hunter Johnson | |
| Nicky Brelaz | Chuck | | TBC | 1.5, 1.7, 3.5 | Frankie Wines | |
| Oliver Wales | Kelly | Dress Rehearsal 2 | TBC | 5.2, 5.3, 7.2 | Alice Georgelin | ⚠️ 5.2 |
| Olivia Wise | Disney Line | | TBC | 1.6 | Evan Quilty | |
| Oscar Balfe | Flugel | | TBC | 2.1, 2.3, 2.4, 3.5 | Eleanor Walker | |
| Oscar Georgiou | Grunge V4 | | TBC | 2.2, 2.4 | Vince Baker-Mayer | |
| Piper Rappell | Death Metaller | Performance 2, Performance 4 | TBC | 2.2, 2.4 | Brendan Black | |
| Piper Rappell | Old Rap Grandma | | TBC | 6.6 | Sarah Duthie | |
| Priscilla Qiu | Back PC 1 | Dress Rehearsal 1, Performance 4 | TBC | 5.6 | Fraser Sue | |
| Priscilla Qiu | Sophia | Dress Rehearsal 4 | TBC | 2.5 | Harriet Bunting | |
| Rebecca Burns | Hyldeguard | | TBC | 7.1 | Felix Carrillo | |
| Rebecca Burns | Stop V1.1 | | TBC | 6.6 | Jess Manns | |
| Remy Havas | Fergy | | TBC | 1.5, 1.7, 3.5 | Jim Swan | |
| Remy Havas | S.A.D. PC | | TBC | 4.3 | Amelia McIntosh | |
| Robbie Haviland | Bella | | TBC | 3.5 | Eleanor De Vere Gould | |
| Rose Brown | Greta | | TBC | 2.6 | Lily McLachlan | ⚠️ 2.7 |
| Rose Brown | Stop V1.2 | | TBC | 6.6 | Olivia Wise | |
| Rosie Briffa | Glad 1 | | TBC | 4.1 | Julian Wu | |
| Rupert Thomas | Toni | | TBC | 1.5, 1.7 | Maya Henry | |
| Ryan Cheung | Judith | | TBC | 6.4, 6.5 | Tiffany Spilling | |
| Sam Leslie-Hughes | Connie | | TBC | 4.2 | Tessa Rice | ⚠️ 4.3 |
| Sam Scadden | Ricky | | TBC | 6.1 | Jordan Gong | |
| Sam Leslie-Hughes | Sixty V2 | | TBC | 1.1 | Milly Waldie | |
| Sarah Duthie | One V1 | | TBC | 3.3 | Zara Willats | |
| Sasha Barden | Neighbourhood People | Dress Rehearsal 1, Dress Rehearsal 2 | TBC | 5.2 | Caitlin Haines, Claudia Wright, Oliver Wales | |
| Scarlett Forbes | Gary | Performance 6 | TBC | 6.1, 6.4, 6.5 | TJ Della-Rossa | ⚠️ 6.2 |
| Scarlett Forbes | Marie | | TBC | 1.5, 1.7, 3.5 | Isabella Cobby | |
| Sihas De Silva | Back V4 | | TBC | 5.6 | Angie Malcontenti-Wilson | |
| Sophie Zhao | Frankie | | TBC | 1.5, 3.1, 3.5 | Julia Hannink | |
| Sophie Zhao | Funk V2 | Performance 6 | TBC | 2.7 | Sasha Barden | |
| Spock Po | Happy B1 | | TBC | 5.1 | Moose Snashall | |
| Sylvie Kahler | Beth | Dress Rehearsal 4 | TBC | 1.4, 1.5, 2.1, 2.2, 2.3, 2.4, 3.1, 3.5 | Alex Lutz | |
| Sylvie Gibbons | Sky V3 | Dress Rehearsal 3, Dress Rehearsal 4, Performance 3, Performance 4 | TBC | 3.6 | Piper Rappell | |
| Tammy Bishop | Doc | | TBC | 3.1, 3.5 | James Talbot | |
| Tammy Bishop | Sky V2 | Performance 1 | TBC | 3.6 | Ada Princep, Abigail Cunneen | |
| Tara Royston | Conga | | TBC | 2.1, 2.3, 2.4, 3.5 | Eloise Witham | |
| Tessa Rice | Pablo | | TBC | 5.3 | Tylar Karabardak | |
| Tiffany Spilling | Dylan | | TBC | 1.3, 1.5 | Matthew Zhang | |
| TJ Della-Rossa | Hot Dave | | TBC | 1.5, 4.2 | Benj Pritchard | ⚠️ 4.3 |
| TJ Della-Rossa | Hoodwink | | TBC | 7.1 | Josie de Vere Gould | |
| Tylar Karabardak | Alex | Dress Rehearsal 3, Dress Rehearsal 4 | TBC | 1.3, 1.5, 5.4, 5.5, 5.6, 5.7 | Hunter Graham | |
| Tyler Mason | Commenteto | | TBC | 1.3, 1.5, 5.4 | Casper Havas | |
| Tyler Mason | Troy | | TBC | 6.4 | Kieran Talbot | |
| Vince Baker-Mayer | Uri | | TBC | 4.2, 7.2 | Amy Lim-Joon | ⚠️ 4.3 |
| Vivi Barhoush | Back V2 | | TBC | 5.6 | Alex Crawford-Paton | |
| Vivi Barhoush | Stop V2.1 | | TBC | 6.6 | Elsa Stanaway | |
| Will Issell | Susan | | TBC | 5.2 | Lilly Scott | |
| William Conn | Giselle | | TBC | 1.5, 6.1, 6.3, 6.7, 7.1 | Charlotte Barry | ⚠️ 6.6 |
| Xavier Jenkin | Audrey | | TBC | 2.5 | Chloe Anderton | |
| Xavier Jenkin | Number Line | | TBC | 1.6 | Benj Pritchard | |
| Zara Willats | Grunge V2 | Performance 2 | TBC | 2.2, 2.4 | Bowie Dekok | |