Jennifer Aniston flips over toilet paper . . . literally.

Yes, the woman named by Forbes magazine as the most powerful star on the planet, the woman who’s married to Brad Pitt and makes $1 million an episode for “Friends,” absolutely cannot STAND it when she walks into a bathroom and sees a roll of TP hung so that the first sheet comes under the roll rather than over it.

She is compelled to turn it over. It’s her No. 1 pet peeve when it comes to doing No. 1 or No. 2.

“If you have it under, sometimes it flies off,” she explains. “I will change the toilet paper if I’m in someone’s house and the paper thing is under. I’ll always flip it.”

And in case you were wondering (and we know you are), Jen’s preference puts her in the majority, according to a national survey. Nearly 70 percent of respondents claim to be in the “over” camp, while 25 percent opt for “under.”