Snake Attack is a Mental Floor 4 Challenge introduced in Series 1.
The Caretaker's explanation to the game:
"A strange wall faces the unfortunates, Hahahaha. One of them must make it safely from one side to the other, choosing which holes to put their hands in. They must choose wisely though, because the wall is home to a hungry child-eating python. She'll be waiting in one of the holes, for a little snack. It's simple. If they get bitten three times, they fail."