The phrase "Mitochondria is the powerhouse of the cell" was coined in a 1957 article by biologist Philip Siekevitz. It apparently rattled around in the English lexicon until 2013, when a tumblr user by the handle apatheticghost posted the following:

what I learned in school

1. I am a fucking piece of shit

2. everybody else is also a piece of shit

3. mitochondria is the powerhouse of the cell

This blew up in popularity and variations emerged that replaced the first two items with various social commentary, but always kept the mitochondria line. It stood for a kind of universal frustration students have with school, that a lot of the curriculum feels like memorizing game show trivia answers rather than useful or practical skills applicable to adult life. Loads of us have no idea how the tax system works but we can all parrot biology factoids.

The phrase became one of those catchphrase in-jokes. A bit like how you can't say 69 without saying "nice" anymore.

My on personal Mandela Effect: I'd swear I'm from the parallel universe where the phrase comes from the Bill Nye The Science Guy theme song, but apparently I'm thinking of "Inertia is a property of matter."