New details revealed in 'It's Always Sunny in Philadelphia' and 'Abbott Elementary' crossover

It's about to be "Always Sunny" at "Abbott Elementary!"

A huge crossover is in the works for iconic Philadelphia shows, and new details have just been released.

"It's Always Sunny in Philadelphia" and "Abbott Elementary" are teaming up for a two-episode extravaganza.

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The gang from "It's Sunny" will be schooled in "Abbott Elementary's" ninth episode this season.

It will likely air in December, and Charlie Day's character is reportedly playing a big role.

Then, the cast of "Abbott" will appear in an "It's Always Sunny" episode next season!

Production is already underway for season 17, which is expected to FX next year.