Back to the Future anyone? C'mon, this is a series of movies that doesn't really appear to be a comedy but it is. As a kid, I always thought it was supposed to be a fairly serious time travel movie, but watching it now, I just laugh my way through the entire thing.
Then there's also Evil Dead 2 and Army of Darkness. While the first movie in the trilogy was a straight-forward horror flick, the other movies that finish off the trilogy are some of the funniest films ever made.
And if it's possible to place Fish Called Wanda and Fierce Creatures together, then you could also make Spinal Tap, Waiting for Guffman, and Best in Show as being another group. While Best in Show wasn't that great (my expectations were way too high), Guffman is the greatest comedy ever made, followed very closely by Spinal Tap.
Oh, I also think that Monty Python movies could be considered a franchise.
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Josef Stalin, hold on to my armor mu-mu, and we shall leave this planet behind.