Why do I find things to be more funny when I'm drunk?

So I've had a few drinks and I'm watching Community. Now, I think it's a funny show when sober, but I rarely laugh out loud while I'm watching it. Right now, however, I can't stop laughing.

I notice it generally - whether in social situations or just watching TV - that I'm much more inclined to think things are funny when I've been drinking. Why is this? What does alcohol do to my brain that makes things funnier?