The movie started out funny and clever. Somehow they managed to make a funny and child-friendly version of Big Brother, and I really enjoyed it. I laughed out loud several times during the first 20 minutes or so.
Then it went downhill.
I was annoyed that the female character was such a blatant Manic Pixie Dream Girl, but fine, whatever. I was very annoyed that she was an even more blatant prize and that one of the jokes had the protagonist not listen to anything she said because he was busy oogling her, but again, not a dealbreaker. Besides, LEGO Batman, that's awesome enough to make up for a lot of annoying things! And the idea of being able to disassemble your world to make anything is fantastic. So far, so good.
The jokes started getting less and less funny. Still not a dealbreaker.
...And then it went live-action.
WHAT THE HELL WERE THEY THINKING???
I go watch a CG movie about superheroes and supervillains and epic battles across fantastic worlds and unlimited creativity and absurd laugh-out-loud humor, and they give me a live-action father-son dramafest in a cellar where the stakes are "daddy doesn't want me to touch his toys"? Are you fucking kidding me?
Extremely, extremely disappointed.