The actor and Quinta Brunson described how the tones of the two sitcoms would mesh and teased which characters would be paired together.

The creator-stars talk about the challenges of merging PG- and R-rated shows and which characters they wish they could keep in their own worlds forever

The respective stars and creators of "Abbott Elementary" and "It's Always Sunny in Philadelphia" discussed how their shows came together for a crossover episode premiering Jan. 8 on ABC.

Kicking off Jan. 8 with 'Abbott Elementary', Quinta Brunson and Rob McElhenney shared details of the 'It's Always Sunny in Philadelphia' crossover.

The biggest moment in Philly television arrives early in the new year with a crossover episode of "Abbott Elementary" and "It’s Always Sunny in Philadelphia" airing on Wednesday, Jan. 8.