Chizzy said, "When I was 13, I made the finals of a disco dancing competition once but there was this unbelievable girl who exploded onto the stage with a gorgeous sequined costume, throwing glitter everywhere..."
The actress left Holby in June after five years as surgeon Mo Effanga.
Charlotte, 42, said: 'Nobody knows, I've kept it a secret from everybody.
2008 victor Alexandra Burke and runner up from the same year, Aston Merrygold of boy band JLS will appear in the BBC One competition.
She was also nominated for "Best Newcomer" at the National Television Awards.
But does she have what it takes to take the top spot on Strictly?
This is my chance to have even more sequins!
When asked if she's looking forward to showing off her moves, The X Factor star Alexandra admitted: "I'm a singer not a dancer!"
Strictly Come Dancing age range of contestants
The actor, 41, previously showed his dancing skills off in 2015 alongside co-star Eleanor Fanyinka in a short sequence titled Holby City Does The Strictly.
Charlotte will be the fourth member of the Good Morning Britain team to try her luck on the show, following in the footsteps of Richard, Kate Garraway and Susanna Reid.
The three join the already announced line-up of Ruth Langsford, Gemma Atkinson, Davood Ghadami, Simon Rimmer, Mollie King, Susan Calman, Reverend Richard Coles, Joe McFadden, Brian Conley and Aston Merrygold.
The final four contestants will be revealed later today.
Retired judge Len Goodman, then surprised the three contestants with a short video, telling them that the only sadness will be that they won't get "Get a 10 from Len".
The forthcoming series will see legendary choreographer Shirley Ballas claim Len Goodman's Head Judge seat following his shock departure at the end of past year and, although the fellow panelists - Darcey Bussell, Craig Revel Horwood and Bruno Tonioli - are excited to have her on board, they're convinced she'll stand her ground.