When you reached Monkey Island and roamed the island for the first time, there was a vulture (or was it more than one?) circling above and quickly descending. For me this is probably the most memorable moment from any game I ever played :)

I often make it a personal goal to finish the Monkey Island parts before the vultures fully descend.

Do you remember when the REAL, living, 3 headed monkey appears?

http://www.youtube.com/watch?v=BXK3_iU0xOA

Yeah, that was funny!