(at around 23 mins) The footage of the X-Men closing the door was shot on the set of X-मॅन: डार्क फीनिक्स (2019) and sent over to the Deadpool 2 crew.
(at around 1h 4 mins) When Deadpool complains about Domino's powers, he says that it must have been the idea of an artist "who can't even draw feet." Domino and Deadpool's co-creator Rob Liefeld is widely mocked and criticized for avoiding drawing characters' feet and hands. (He also reportedly loved that joke.)
Ryan Reynolds was at a dinner party with Matt Damon, pitched him the toilet paper manifesto, and asked Damon if he wanted to play the part. Damon thought it was hilarious and agreed to the cameo.
(at around 1h 8 mins) The gag where Deadpool stops Cable's bullet with a sword and then uses both to "stop" multiple bullets only to realize many of them made it through to his body was conceived by the stunt team. David Leitch passed on it initially as being too comedic for a dramatic sequence, but when he showed it to Ryan Reynolds the actor found it hilarious. The entire sequence is a reference to an infamous scene in 'X-Men Origins: Wolverine' where the watered down version of Deadpool (also played by Reynolds) successfully deflected many bullets in this way.
The film takes many potshots at the Barbra Streisand film Yentl (1983). Streisand is Josh Brolin's stepmother in real life. Although this fact would have been a perfect subject for another meta-joke at Brolin's expense, the makers stated on the commentary track that they completely forgot to include it, wondering how that was overlooked.
Matt Damon, Alan Tudyk: Two rednecks whose truck Cable steals. Damon, who is unrecognizable under heavy prosthetic makeup, is not credited under his own name but as "Dickie Greenleaf," the name of Jude Law's character in The Talented Mr. Ripley (1999), who is murdered and then impersonated by Damon's character Tom Ripley.