Animated. A group of kids use a time machine (in their garage if I remember it OK), they travel to prehistoric times where they meet a creature who looks like a vacuum cleaner (I know, right?), or Gonzo on four legs (but with suckers, so he can e.g. walk on the ceiling). They bring it back to today, it lives with them but they must keep him a secret. They wrap him in some blanket whenever they go out with him at night. Also, when he holds his breath, he may levitate like a hellium baloon. He eats eggs, I think, and in his original times he has a storyline with a pterodactyl and his newborn youngs.
Please tell me I wasn't hallucinating as a kid :) Also, It might have been a TV show, because I watched it on a video tape over and over. But I doubt it.