Tensions were high during Abbott Elementary‘s crossover episode, but Charlie Kelly (Charlie Day) learned a valuable lesson. The satirically bad people of It’s Always Sunny In Philadelphia visited the elementary school as volunteers, but a running gag from the FX series came to a head early in the episode: Charlie’s illiteracy. While the rest of the “Gang” consisting of Dennis Reynolds (Glenn Howerton), Deandra “Sweet Dee” Reynolds (Kaitlin Olson), Frank Reynolds (Danny DeVito), and Ronald “Mac” McDonald (Rob McElhenney) were causing chaos around the school, Charlie was ironically the calmest It’s Always Sunny In Philadelphia character there.

https://screenrant.com/abbott-elementary-always-sunny-crossover-charlie-read-fate-perfect-op-ed/