Family Guy has possibly one of the most obvious in jokes ever, Adam West as Mayor Adam West who has frequent delusions about crime fighting etc, and being prepared for things (a'la Batman/Batbelt).
After the series restarted they had a scene where Peter is saying to Louis that the series is cancelled and she asks if there is any chance of it coming back, and he lists the programmes that would have to be cancelled for that to happen (a long list of shows that were cancelled by the network between the end of the previous series of FG and it's return).
A few Anime in jokes/references
In Gunbuster (Made by Gainax who are major anime fans), there are various posters, one being Totoro above the main characters bed.
One of the secondary (American iirc) characters is named after an American who was visiting on a licensing trip.
The method of entering FTL travel was called a Tannhauser Gate, after a reference in Blade Runner.
On a related note in Star Trek The Next Generation there is a species of sentient whales called Takaya's Whales that are named after the main character in Gunbuster (which had whales/dolphins serving as navigation crew in one episode), I don't think they were ever mentioned specifically on screen but there were references to "Cetacean ops" in the TV series and were on some Galaxy class ships (I think they are named specifically in one of the books).
Apparently one of the writers is/was a big fan of Gubuster.
Talking of ST:TNG - apparently a lot of the consoie text was jokes/references to cast and crew from memory, but was rarely if ever readable.
From memory in Serenity there are several boxes with the label "Do not dispose of, reusable" which is apparently a reference to the fact that (from memory) despite Whedon asking/warning that the set/props should not be disposed of after Firefly got cancelled, the props were disposed of (so they had to rebuild much of the set and many of the props for the film).
If you just want references to other shows, then the opening to Daicon III and IV in 81 and 83 (big Japanese sci-fi con), an animation made by several students who went on to found the Animation Studio Gainax, would probably be very hard to beat.
It's got hundreRAB of references to everything from Metropolis, Conan and Forbidden Planet, through to Star Wars and Aliens, with pretty much every major Sci-fi series/film/comic/anime of the time represented (one sequence has the main character flying over a crowd of characters, in another she's fighting Darth Vader, Godzilla, and in another the Enterprise is blown up alongside the Yamamoto).
I tried counting them once, and got to about 200 characters/ships I recognised (not including the fact that the main character was wearing a red bunny girl outfit, and in a flying Daicon radish), before I gave up. For Star Wars alone there was Darth Vader, Storm Troopers, the Deathstar, Yoda, Tie fighters and I think a Star Destroyer.