She went on: "I think I've got to be the only Welsh actress who has never been in Doctor Who so if someone would like me to be in Doctor Who I'd love to have a part."
The actress was at London's Apollo Victoria Theatre to support friend Louise Dearman, who recently took over in the role of good witch Glinda.
Joanna said she was "blown away" by her pal's performance, and revealed she'd be keen to tread the boards in a musical herself.
"I'd love to do a musical - I haven't got the voice to be in Wicked. It would have to be something I can act in."