Movie making has got to be an absolute blast. There's no other explanation for how pretty much every movie you've ever seen has some kind of weird joke hidden inside it just as an Easter egg for fans, obsessive compulsives, or in some cases, even the film-makers themselves. Below are all examples of actors, stunt-people, writers, and directors all making references to their previous work.
Jeff Bridges in Iron Man/The Big Lebowski
In the first Iron Man movie, as Pepper Potts (Gwyneth Paltrow) is trying to steal some information from Obadiah Stane’s (Jeff Bridges) mainframe, there’s a brief reference to an earlier film starring Bridges - it’s only one frame long, but it clearly says “Lebowski” and lists the origin port as “Long Beach,” making it a clear reference to Bridges’s much-loved role as Southern California burnout Jeffrey Lebowski in the Coen Brothers’ The Big Lebowski.
It’s an especially funny comparison since Obadiah Stane and Jeff Lebowski are pretty much polar opposites. The former is a multi-billionaire evil industrialist, the latter is... is uh... is this a... what day is this?
The Nicholas Cage Beige Volvo Trilogy
Here’s a neat one that I found on TVTropes: Apparently Nicholas Cage really likes beige cars. He says he drives one in The Rock. Later, he drops Dave Chapelle’s body into one in Con-Air.
Proving that.... Nicholas Cage loves beige Volvos? If James Cameron ever directs a movie where Nicholas Cage bites Michael Biehn's hand while driving a beige Volvo then... then we'll really have something here.
Steve Carell in The 40 Year Old Virgin/Evan Almighty
The 40 Year Old Virgin wasn’t that good, so you have to be in a really s**tty movie to want to go back to it. Luckily, Evan Almighty was a really s**tty movie.
I guess none of us are really “lucky” to be subjected to that kind of pun.
Jeremy Irons in Lion King/Reversal of Fortune
No one plays “Creepy old guy” like Jeremy Irons. In The Lion King, when Simba says “you’re so weird,” Scar’s haunting response (“You have no idea”) would have been strange and foreboding even if it hadn’t been a repeat of the same line from an older film, Reversal of Fortune, where Irons played an arrogant and aloof British socialite accused of murdering his wife.
Which is actually not all that different from the plot of The Lion King... if you’re crazy. Or if you’re the person who made this (and are also crazy).