Especially since the Season 3 cast includes celebrities like Denise ... She once played a military school captain in Cadet Kelly, but who likely knows very little about real training.

Once she was asked to join the cast, however, her old alter ego kicked ... aside from dancing as a kid and completing a boot camp before filming Cadet Kelly. Luckily, her husband, Brendan Rooney ...

Christy Carlson Romano, former Disney Channel star of “Kim Possible,” “Even Stevens” and “Cadet Kelly,” grew up ... little tougher than most child actors,” Romano said.