Mind Control Helmets are devices used by Blitzen in the second Robbie the Reindeer film Legend of the Lost Tribe.
He puts them on Donner, Prancer, Old Jingle and the other reindeer to turn them into robots and use them as attractions for his theme park "Blitzen's Reindeer World".
Whilst wearing them, the reindeer do not feel pain (e.g. Donner, Prancer and Tapir get stamped on by a giant fake dinosaur foot and it does not harm them). However Blitzen does not put one on Robbie (who is hung above a pit full of bear traps) as he wants him to feel every moment of it.
Luckily a tribe of Vikings Robbie befriended arrive and free him and Robbie leaves to save the other reindeer. He is able to remove the helmets from them and they regain their senses.