It's crazy. We'll have her swaddled and yet somehow she can still wriggle herself from one side of the crib to the other. The other day I left for less than 5 minutes and when I came back she had turned herself a full 180 degrees and had her head against the slats. This is why I'm scared to put her in the crib at night, although she does wriggle around in the cosleeper too.
Due 12/20/11 ~ Lost our Muskrat at 9w2d
4/25/12 ~ Our angel, Persephone James, is here!

Re: My baby can do the Worm
4/25/12 ~ Our angel, Persephone James, is here!
My daughter does the same thing - also sleeps swaddled and somehow manages to be in a completely different spot in the crib when I get up to feed her, sometimes all the way against the bars.
Don't worry too much though. She might manage to bump her head, but she can't move her body with enough force yet to really hurt herself doing it.