When you're acting in a movie, you never consider the reception of it. It's impossible to predict how something will be received. Even if you think it's the greatest thing in the world, other people might not like it. Or agree with it.
In 'Zombieland,' it was such a freewheeling plot it almost didn't matter what the characters were doing scene to scene as long as there was a consistent banter.
I guess the more serious you play something, if the context is funny, then it will be funny and it doesn't really require you to be necessarily, explicitly humorous, or silly.