Sugababes singer Berrabah and ex-Girls Aloud star Harding will join other British celebrities, including Steps singer Ian 'H' Watkins, super-middleweight boxing champ Carl Froch, and veteran fitness guru Mr. Motivator in new Bbc show Tumble.
The contestants will train with professional gymnasts to perfect tricky routines they will then showcase on the programme before a viewers' vote decides who stays and who goes.
Harding says, "I'm really looking forward (to it), but also a little bit scared about all the training I'll be doing - but at least it beats going to the gym."
Tumble is scheduled to air later this year (14).
Many ticket-holders couldn't get into the O2 Arena show on Tuesday night (September 19th) because they didn't bring photo ID to match their booking.
An album re-release, a new song and a documentary mark the singer's legacy this year.
The film will be the first in the Marvel Cinematic Universe led by a person of colour.
The actor plays the titular hero in the forthcoming adaptation.