Humpday isn't exactly the sort of movie that spawns a franchise, but here's the closest thing: The Freebie, about a similar kind of mumblecore couple in comically sexual crisis. It's even directed by -- and starring -- Katie Aselton, the wife of Humpday star Mark Duplass.
Aselton and Dax Shepard play a young married couple who start exploring the idea of a very limited, non-monogamous window. Since they got married young and they're still kinda hot and hip, what's the harm in an isolated one-night stand, they figure? It looks cute and appealing -- and sure, Humpday-ish -- so as long as the eventual agita and sexual recriminations aren't that heavy, I guess I'm in. It's like the fun, broke version of Indecent Proposal, kind of!
VERDICT: Sold.
The Freebie Movie Trailer [Slashfilm]