I just stumbled upon up the Wilhelm Scream, and the number 47. And even though they are apparently widely known, I had never heard of either. what other well known injokes are out there that I might be missing?
That would be telling.
Animation directors John Lasseter and Brad Bird both sneak the number A113 in all their films, the room number of a CalArts classroom.
John Landis always puts in the phrase “See you next Wednesday,” the title of an early film of his.
I don’t know if it’s a gag, but the name Alan Smithee was used by directors and other members of the film industry when they no longer wanted their name on the finished product.
Must not forget 42.
And don’t forget your towel!
It wasn’t a joke- it was an actual DGA policy. It eventually became common knowledge, though, and the DGA no longer allows directors to use the psuedonym.
Klaatu barada nikto.
Is this somehow related to the phrase “See yoU Next Tuesday”? (replace “see” with the letter “C”, add up the capital letters, and you’ll get it…)
I was thinking the same thing. I have no idea.
My apologies to Matt Damon, we ran out of time.
If you wonder why the fanboys get all giddy and wrestless in their seats at the movies when some old man appears in a bit part it’s probably Stan Lee making a cameo.
Then there’s the whole 4:20 deal the potheads like and why all the clocks in Pulp Fiction were set to it.
Which of course led to Sarah Silverman fucking Matt Damon…and Jimmy Kimmel fucking Ben Affleck.
never mind
Well, there’s always “The banana gag.” But you really have to see it, it can’t be explained.
Is that any relation to the…ha ha ha ha…the…ha ha ha…the Banan…HA HA HA…Banana Sketch? Sorry, makes me laugh just thinking about it.
That’s right! You’ve got it. I knew I wouldn’t be able to do it justice if I’d tried. 
You might have heard of a shadowy group of conspirators known as the Illuminati, but no such cabal actually exists.
Hitchcock had something similar going on. Bathrooms, and/or the initial “BM”, in just about everything he did. It’s listed as a “director trademark” on many of his IMDb listings.