A crossover fans have been asking for is in the works. In a recent Instagram post, creator and star of “Abbott Elementary” Quinta Burson poses with ‘It’s Always Sunny in Philadelphia” stars Rob McElhenney and Charlie Day. The caption reads: “Season 4 of Abbot Elementary gets real Sunny.” McElhenney also added an additional photo on his own on social media, which includes ‘It’s Always Sunny in Philadelphia,” stars Danny Devito and William Stanford Davis and Tyler James Williams of “Abbott Elementary.” The news follows months of speculation but makes sense because both shows are based in Philadelphia. Plus, Brunson and McElhenney are both from the City of Brotherly Love, making this the ultimate crossover. It is still unclear how the two hit shows will merge. “Abbott Elementary” returns for Season 4 on Oct. 9, while Season 17 of “It’s Always Sunny in Philadelphia” is in production. Sign up for our Breaking newsletter to get the most urgent news stories in your inbox. This story uses functionality that may not work in our app. Click here to open the story in your web browser.