Actually if you consider Munna bhai an original movie then you are wrong! Munna Bhai itself is based on the 1998 hollywood movie titled Patch Adams, which depicts the trule life story of Patch Adams. Dont even say that Munna Bhai is being copied when the movie itself is a copy!!
Actually no, Patch Adams is completely different. For starters, the protagonist in Patch Adams is actually a doctor while in Munnabhai he is just pretending to be one. The entire premise is different.