Very, very hungry.
One is 6 people singing 100 songs, the other is 100 people singing 6 songs.
When there is no "L" ("Noel")
If she's only wearing one sock. (This joke brought to you courtesy the homeless guy outside my local 7-11.) Edit: tweaked the punchline.
Only 2, but I have no idea how you're gonna fit both of them inside a lightbulb.
