On Star Wars tie ins-it isnt really a big leap given the popularity of the toys at the time but what i find irritating is when a filmmaker constantly references his own work or that of a friend--Spielberg and Lucas did it a few times, especially in the 80s.
I actually quite like that kind of stuff. I suppose in a way it could be interpreted as being somewhat elitist ('Oh did you spot the reference?' - 'Oh no, well I did.'), but it's something I've always enjoyed in books particularly by authors like Ballard, Will Self and Bret Easton Ellis.
It's a sort of nudge and wink to themselves, but also the readers and viewers and more obviously the fans/geeks.