I can fit an alarming amount of my little finger into my belly button.
But that's probably because it bends the wrong way.
( Malchick, Fri 12 Jan 2007, 22:30, archived)

*experiments*
If I push, I can fit the whole finger in, right the way down to the base.
Without pushing, it goes in up to the first knuckle.
( Comma, Fri 12 Jan 2007, 22:34, archived)