Phineas And Ferb: Season 3, Episode 30

3 - 30:

After Mom asks the kids to keep quiet while she prepares for her online knitting test, Phineas and Ferb create ninja outfits designed to hide the wearer from anyone who is not wearing them. Meanwhile, Candace becomes increasingly frustrated after she can't find the boys and bust them. Across town, Dr. Doofenshmirtz invents the De-Handsome-Inator.