I found some humorous BE in the Negima Manga. Anya, Negi's childhood friend is ashamed that her breasts are much smaller than, well, basicly anyone's. She then proceeds to cast a spel on both her and her 'friend' Nodoka to increase their breast size.
http://www.onemanga.com/Mahou_Sensei_Negima%21/183/07/
Not great but funny.
-Iscariot