To understand this theory, first you need to understand how my ideas of continuity within the Muppets works. There is the Muppet "real world" in which the Muppets are essentially an acting troupe. The "Real World" for the Muppets can be seen in the "behind the scenes" segments of The Muppet Show and Muppets Tonight, along with certain movies and specials, like the very beginning and end of The Muppet Movie and the most recent Muppet Movie.

Then there is the "stage" Muppets, which consists of the Sketches on the shows, along with movies like Muppet Treasure Island, Muppet Christmas Carol, and The Great Muppet Caper. (I'm not really sure where The Muppets Take Manhattan or Muppets from Space takes place so I am not listing them).

In 2002, NBC did a Muppet Christmas special called (appropriately) It's A Very Merry Muppet Christmas Movie. It is pretty much It's a Wonderful Life for Kermit. I have not actually seen this movie, but from what I have read it seems to take place in the "Muppet Real World". In this scene (http://www.youtube.com/watch?v=g1_mC9tf--M) from the special Miss Piggy is cast as an extra on Scrubs, indicating that in the Muppet Real World, Scrubs is just a TV Show.

Fast forward to this scene from Cougar Town (http://www.youtube.com/watch?v=kuPr5lvCOzk) in which Ted from Scrubs guest stars, indicating that Scrubs and Cougar Town take place in the same universe.

Now the final link in this chain is Community. One of Abed's favorite TV shows is Cougar Town. Since Scrubs, and by relation Cougar Town, is a TV show in the Muppet Real World, and Cougar Town, and by relation Scrubs, is a TV show in Community, one could reason that the Muppets and Community are in the same universe. Or they are in two different universes with similar prime-time schedules.