Revealing mistake: When the kid who breaks the egg throws it out the window, the egg hits another egg which starts rolling down. You can see the tracks on the grass making it easier for the egg to roll. (00:30:05)
Revealing mistake: When a ball of about four Critters is rolling, after coming out of the antique shop, you can see the wires that are pulling it.
Revealing mistake: When the bounty hunters are landing the ship, look closely, you can see the wires holding it up. (00:36:30)
Revealing mistake: Nearing the end of the film when the giant critter ball is roll back to town and the good guys are following in the truck, you can see the shadow of the truck in front of the critter ball pulling it along. It's visible in more than one shot.
Answer: From what I recall, Charlie followed the bounty hunters as they walked away in the first film. So the implication is that they decided to let him tag along with them. (And that makes sense. After all, he helped them destroy the Krites in the first film, so he'd be useful.)
TedStixon