Checking the wiki, it would seem to also include Emmet Otter's Jug Band Christmas, The Land of the Gortch, The Animal Show, Big Bag, The Tale of the Bunny Picnic, Panwapa, The Electric Company, Captain Kangaroo, H.R. Pufnstuf, Mister Roger's Neighbourhood, Kukla, Ollie, Gophers!, Splitting Image, Soul Man, Cosby, Between the Lions, Bear in the Big Blue House, The West Wing, PBS Kids, Mr. Magorium's Wonder Emporium, The Sunny Side Up Show, Scrubs, 30 Rocks, So Random (and the rest of the live action Disney Channel shared universe), and pretty much every international version of Sesame Street. There were a few times where the Wiki didn't list the crossovers, only saying there were "many" so there's definitely more. A lot of these could also most likely be impossible to happen, but it'd be nice to attempt something like this still
Sorry for the wall of text, TL;DR The Muppets have crossed over waaaaay too many times
these were only the Muppets crossovers, too. To name one Sesame Street one, they're implied to exist in the Alf episode A.L.F., which I guess would bring The Big Bang Theory into it?
Dozens of characters have paid visits to Sesame Street, including Batman and Superman, C-3PO and R2-D2, Bugs Bunny, the Pink Panther, the Wicked Witch of The West, the Fonz from Happy Days, Wayne from Wayne's World, Tyrion and Cersei from Game of Thrones, Delores and Bernard from Westworld, the Simpsons etc.
Since they acknowledge the Muppet show as a show, and the Muppets Movie (the one with Walter or whatever the new guy's name was) as an in-universe movie, and the nature of Sesame Street, I'd say Sesame Street is (to an extent) an in-universe show, so anything that literally can't happen (eg Star Wars, DC) is most likely parody. A lot of the things listed weren't true crossovers anyway (eg the Wicked Witch one was only the actor, Pink Panther only references Sesame Street - most likely as a show) but there are still a lot of ones that could work - Happy Days, Bug's Bunny, to name a few (I'm not sure how Bug's Bunny did it, but it'd most likely be WFRR/Space Jam Bug's Bunny anyway, so I fortunately wouldn't have to add dozens of Warner Bros. cartoons)
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