How about a episode where the spotlight is shown on the genre of comedy? Often compared with the horror genre in how subjective both are in terms of what makes a person laugh versus what makes a person afraid, it'd be interesting to hear what some of Ted, Tony and/or Doug's favorite comedies are and what kinds of comedies in particular they find themselves drawn to. TV shows, books, writers as well as comedians (also podcasts!) could also be touched upon as well.
A particular documentary (and book) that also may be of some usefulness here is "Make 'Em Laugh: The Funny Business Of America" ("History of the Joke with Lewis Black" might also be another one to check out). There are also of course tons of documentaries and books out there on specific comedians as well as groups of them performing together as well.