SPOILER WARNING: The following article contains spoilers for Deadpool 2, in theaters now.
One of the best-remembered gags in 2016's Deadpool sees the Merc with a Mouth remark that the normally-bustling X-Mansion is largely deserted because Fox didn't have the budget for more X-Men to appear.
Ryan Reynolds' character makes the same joke in the sequel as he returns to the similarly vacant School for Gifted Youngsters...with a twist: Unbeknowst to the loud-mouthed superhero, the annoyed X-Men do briefly appear on-screen before Beast hastily closes the room's doors to avoid further interruption.
In an interview with ComicBook, co-writer Rhett Reese revealed that X-Men: Dark Phoenix director Simon Kinberg actually directed the blink-and-you-miss-it cameo instead of Deadpool 2 director David Leitch.
"That was actually facilitated by Simon Kinberg who was shooting Dark Phoenix and actually shot that up in Montreal, and we green-screened that in, in Vancouver," explained Reese. The Kinberg-filmed cameo has Nicholas Hoult's Beast, James McAvoy's Professor X, Tye Sheridan's Cyclops, Alexandra Shipp's Storm, and Evan Peters' Quicksilver all appear uncredited.
While the upcoming X-Men movie was filmed the same time as Deadpool 2, helping make the cameo possible, its release date has been pushed back to 2019.
"It was such a tent pole joke of the first movie, us being the underdog, the studio would never throw us any other X-Men except the minor characters," observed Reese on adding the cameo. "We thought, 'How fun would it be to have everyone in the room and Deadpool not see them.'"
Directed by David Leitch, Deadpool 2 stars Ryan Reynolds as Deadpool, Brianna Hildebrand as Negasonic Teenage Warhead, Leslie Uggams as Blind Al, Stefan Kapičić as the voice of Colossus, and Karan Soni as Dopinder, with newcomers Zazie Beetz as Domino, Josh Brolin as Cable, and Julian Dennison as Russell. The film is out in theaters now.