In one shot, we could clearly see Aaron's leg sticking out from the blanket. When it cut to a different angle, no leg. I think it means that Aaron's leg can stretch or shrink or become different shapes. He's a shapeshifter. It's really the only explanation.

WOAH! Put that in a spoiler font, geez! So Aaron is an Other/survivor/shapeshifter/nanobot. NOW IT ALL MAKES SENSE!

heh, thats the best catch of the episode, you deserve an award or something.

Or it could mean that they actually have real child and a doll playing Aaron and they were switching them around...

it was continuity error. :P

That seems too bizarre even for this show! :)