What homages/references have you seen of Nintendo characters/themes/etc. in other games?
Today, I was playing Sam & Max (Season 2, Episode 1 - Ice Station Santa) and was delighted to see an arcade sequence based on Punch-Out!! The gameplay mechanics were very much the same, the music was clearly based on the Punch-Out!! theme, and the second opponent is named "Bald Bullrat". (Yeah, I added this to the trivia section of Mike Tyson's Punch-Out!! on Wikipedia...) I thought that was really neat!