Here's some background and inside jokes to help fill in some of the gaps for viewers who don't watch both Philly-based shows.

The cast of 'It's Always Sunny In Philadelphia' (CREDIT: Tibrina Hobson/Getty Images) Two sitcoms have collided in a new clip from Abbott Elementary, where they meet the cast of It’s Always ...

The star of the FX series also admits he was initially hesitant about the crossover concept as 'It's Always Sunny in ...

The cast of It’s Always Sunny in Philadelphia made its way to the ABC show, which is set in Philly, for the crossover episode of comedy writers’ dreams. The brief promo for the Jan. 8 ...

As of Jan. 9, the episode is available to stream on Hulu. The second crossover is expected to be an episode of "It's Always Sunny in Philadelphia," which has aired on FXX since 2013.

Their next test? When the cast of “Abbott Elementary” appears in an episode of “It’s Always Sunny in Philadelphia,” as is planned for the coming season. We now know that the “Sunny ...

Charlie learns to read, Dee impersonates Ben Franklin, and Frank fights raccoons. We don't quite know what's up with Dennis though.

The hit ABC sitcom is joining forces with the cast of FX's "It's Always Sunny in Philadelphia" for a two-part crossover that's sure to bring plenty of belly laughs. The collaboration commences ...

When will the It’s Always Sunny in Philadelphia episode air? While we know for a fact that the Abbott Elementary episode of the two-part crossover event will occur on January 8, the exact date ...

The "It's Always Sunny in Philadelphia" crew is headed to "Abbott Elementary" in the first of two crossover episodes.

A new “Abbott Elementary” episode brings volunteers from “It’s Always Sunny in Philadelphia.” The crossover episode airs Wednesday, Jan. 8, at 8:30 p.m. ET on ABC.

The Abbott Elementary and It’s Always Sunny episode titled "Volunteers" will see the Always Sunny characters brought in as volunteers to “help” the Abbott staff. It seems the whole Paddy’s crew — Rob ...