"The Monster of Phineas-n-Ferbenstein" - Mad scientist turns himself into a fairy princess twice, and near the end the female antagonist transforms into a brute. Little process, but for those who are interested...
Part 1 (off-screen fairytization at 4:50)
Part 2 (poofy fairy TF at 4:25, monster process at 5:35)
Full Episode (3:45, 8:15, 9:20)
And just in case anyone's missing it, here's "
Attack of the 50 Foot Sister" as well. It's actually a pretty cute uneven growth sequence. She starts growing at 3:50, then her nose grows bigger, then her head, then her tongue, then at 5:00 she evens out. Then at 9:50 everything in the universe grows to match, which I guess can count if you want it to.