I was watching this tiny cut I made from the show:
and suddenly realized:
Giving Pinkie Pie the tickle treatment would render me unable to stop, even if I wanted to.
I thought: It would be a vicious cycle and the metaphor of turbocharging came to my mind.
Then I realized that the metaphor is more appropriate as I thought at first, because the thing that prevents a turbo engine from blowing up is the so-called "wastegate".
And what will ultimately happen if you keep tickling someone which will put an end to any kind of fun? ... A wastegate opening.
Not sure how effective that would be specifically in the case of Pinkie Pie though. Her element of harmony is among the most powerful forces in the universe.
(Maybe that's why the Nazis couldn't resist using tickle torture, haha. Perhaps they were performing experiments in order to create the deadliest joke ever which would make people die laughing.)
But I digress.