This article contains spoilers for Abbott Elementary season 4 episode 9 Volunteers.At first glance, a crossover episode between Abbott Elementary and Its Always Sunny in Philadelphia makes all the sense in the world. Both comedies are beloved by their respective fans, set in the City of Brotherly Love, and most crucially: air on networks (ABC and FX) owned by the same corporate parent (Disney). There is, of course, that one little hang up. It just so happens that Abbott Elementary is a warm PG-rated fable about the power of friendship and public education. Its Always Sunny in Philadelphia is a jet-black narrative about five of the most selfish and degenerate people who have ever lived. To put it mildly, theres a bit of a tonal imbalance at play here. So much so that Abbott Elementary creator and IASIP fan Quinta Brunson has all but begged her shows audience to tread carefully when venturing out to sample Its Always Sunnys 16 (and counting) seasons. It remains to be seen how Abbott Elementary die hards respond to Always Sunny once they get into the shows immense catalogue on Hulu (or Netflix in the U.K.). One things for sure though: they will make the attempt. Because Abbott Elementary season 4 episode 9 Volunteers, the first of two planned crossovers between the shows, is a sublime TV-watching experience. Like the best TV crossovers, Volunteers has a way of highlighting each programs strengths while still maintaining the tone and formatting of the host show. In the case of this crossover, that means the visiting characters from Paddys Pub on IASIP have their rough edges slightly sanded down for a fruitful, yet mostly family-friendly trip to Willard R. Abbott Elementary School. The arrival of Mac (Rob McElhenney), Dennis (Glenn Howerton), Charlie (Charlie Day), Dee (Kaitlin Olson), and Frank (Danny DeVito) also gives the characters of Abbott Elementary to expand their comedic horizons a bit. Mr. Johnson (William Stanford) matter-of-factly stating that his school is named after an old racist isnt unusual for the tone of the show. What is, however, is the old racist receiving the news responding with no trace of discomfort. Janine (Brunson) must level her game up immensely when Dee expresses a romantic interest in Gregory, completely unconcerned by his relationship status. Watching the diminutive Janine go toe-to-toe with the statuesque (or ostrich-esque) Dee is a real delight. Similarly, Melissa (Lisa Ann Walter) gets off an honest-to-goodness ass-eating joke. She goes on to clarify that she is a bear in this scenario and will be eating the rest of Goldilocks too but what a moment for ABCs censors. Of course, this being an actual episode of Abbott Elementary, Volunteers is more about incorporating the Sunny crowd into the schools cheerful orbit. This is easier said than done. Frank Reynolds, God bless him, eats dirt, gets trapped in a raccoon cage, and sleeps under a piss-soaked blanket. The show also doesnt even make an attempt to humanize Dennis, with the five-star man announcing that he knows quite a bit about filming and consent and ducking away from the cameras. While Dennis absence is largely due to Howertons limited availability as hes filming the Netflix series Sirens, its also probably for the best. Of all the Sunny characters neuroses, Dennis serial killer vibes would be the hardest to introduce into network television. Thankfully, Its Always Sunny in Philadelphia features a character who has truly belonged on Abbott Elementary this whole time. Charlie Kellys transparent illiteracy has long been one of IASIPs funniest running jokes. While all of the shows players are ignorant and undereducated to differing extents, poor Charlie never quite got the hang of reading. He was always more interested in topics like milk steaks, bird law, and little green ghouls than books. His inability to sound out words always livens up a scene. (Note that in the first clip of the following video Charlie is wearing the very same jacket he eventually wears on Abbott Elementary.)Charlies illiteracy has grown both funnier and sadder as the show has gone along. While the characters were all 20-somethings when Its Always Sunny in Philadelphia began, four of the five actors in the main cast are now pushing 50 years old while the ageless and sprightly DeVito hit 80 last year. A 47-year-old janitor who cant read offers up a a far different comedic dynamic than a 25-year-old janitor who cant read. Like it often is, Its Always Sunny in Philadelphia was accidentally on the cutting edge with this silly joke about one of its characters. The United States is currently in the midst of an adult literacy crisis. According to a National Center of Education Statistics study, one-in-five American adults were found to be functionally illiterate while more than half of American adults read at below a sixth grade level. Given the talent and social awareness of Abbott Elementarys writing staff, it was only a matter of time before the show opted to address the literacy crisis. How lucky were they then to suddenly gain access to one of televisions most beloved illiterate characters!Melissa, Barbara (Sheryl Lee Ralph), and Jacob (Chris Perfetti) taking an interest in Charlies education is undeniably wholesome and sweet. Charlie goes from not being able to read a hall pass to being able to rattle off facts about birds, his favorite topic. When Principal Ava (Janelle James) asks Whats happening in here, is someone walking on water?, Jacobs response feels earned and accurate: Even better, we taught one of the criminals to read at a kindergarten level.Join our mailing listGet the best of Den of Geek delivered right to your inbox!Whether Charlies newfound literacy sticks in Its Always Sunny in Philadelphia season 17 remains to be seen. He already struggled a bit at the end there differentiating between Guest and Ghost. But for one glorious episode of television, Charlie Kelly: King of the Rats got the empathetic treatment he deserves. The Abbott Elementary crossover episode with Its Always Sunny in Philadelphia is available to stream on Hulu now.