Rugrats (1991)

Season 3: Episode 6

Playing doctor (not THAT kind of playing doctor) with her ""Binks McGill"" doctor kit (based on the TV show), Angelica diagnoses Chuckie with the entirely ficticious ""Rhinoceritis"", in which Chuckie will turn into a rhino. The signs of ""Rhinoceritis"" includes a bump on a head (where ""a horn is growing in""), scaly skin (actually, scabs), and ornery behavior. Meanwhile, Drew helps Stu and Didi with their income tax, with some sound advice for those who don't file properly.