That's what I really enjoyed as well. It's got some really fantastic slapstick comedy all over the place, and I was usually laughing throughout, but there was an underlying discomfort that I had through almost the entire movie, and there are enough emotional beats here and there to keep it from being vapid like, say, Evan Almighty. Very similar to Charlie Kaufman's work, in the sense that it's not all goofiness and it's not just a genius concept; it's relatable and the execution is pretty much flawless.
It’s almost uncanny how well it balances the high-concept premise and humor with the heartbreaking drama
On another note, I should just take a moment to respect the music used in this film. Philip Glass is ace.
And now I understand the origin of this gif: