With more than one occurrence each of paintball and musical episodes and alternate timelines, among puppetry and claymation and many other ideas that most shows would consider too daring, there is a lot of interesting material to make funny. Instead of the usual comedy format of cramming jokes into everyday life in the same two or three locations, Community takes the basic logistical idea (with Greendale and Troy and Abeds apartments the two most common sets) and keeps it fresh with the different genres that get thrown into the mix.
The puppet episode from season four is my favourite example of this. With callbacks to recurring ideas from the whole series, such as Troys has anyone else noticed Professor Duncan hasnt been around for a long time? after John Olivers unexplained disappearance from the show, and Pierces I never slept with the great Eartha Kitt after all his previous anecdotes. Equally, the darkest timeline of Remedial Chaos Theory leads to the wonderful moment when Troy returns to the apartment with the pizza to discover the ridiculous and horrifying scene that erupted after his departure and his facial expression is absolutely perfect and is all thats needed. This is the type of comedy that wouldnt fit into normal half-hour comedy shows.