The Purple Tentacle skip

The Purple Tentacle skip is basically the same as the Green Tentacle skip... only you can't switch to a different kid once you've entered the room where the Purple Tentacle is! That means, we need a cutscene. Keep a kid outside and, before entering the secret lab door, switch to this kid and ring the doorbell. Then, switch to the kid who's next to the secret lab door, enter it, and wait for the cutscene that shows Ed wondering whether his package has arrived. Once you've skipped the cutscene, you can move to the right and the Purple Tentacle won't bother you.