This can and does come up when, say, you have a team for 10 year olds and one of the kids looks like they drove themselves to practice. A coach can challenge the other team’s paperwork, in which case the challenged coach digs it out and everyone looks at the evidence. If it seems to be faked and the umpire agrees, the cheating team forfeits, and the kid’s parents (and possibly the coach if they were in on it) can be banned.

No, Little League doesn’t do a top secret clearance check on every player. Individual players may be checked if it’s believed they’re cheating though.