I think it's cool (or can be) when TV/movie directors and producers throw in allusions/homages to previous works. Like in Coming to America, when we see the two (now bankrupt) Duke Brothers from Trading Places out on the street. Or when guys like Chris Carter and Christopher Guest keep using the same character actors in their shows/films.
It's even better when it's subtle. Tonight on Alias, there was a party scene where the faint background music was a song by Drive Shaft, the fake band from J.J. Abrams' other hit show, Lost. Smooth.