In The Shining it was discovered that Jack Nicholson used to be a fire marshall when he left the set to sift through the remains of the WTC to find his coworkers after 9/11.
In Chamber of Secrets (2002), Harry heals and gets better even though he spits out the Skele-Gro potion. This is referencing the fact that young boys don't need any magical help to grow hard bones.
In Percy Jackson: Sea of Monsters (2013), Grover mistakenly gives Percy credit for quests he never did, this is because, like the film makers, Grover never read a Percy Jackson book
Before the actors' strike in 2023 and the writers' strike in 2007, there was the lesser-known decors' strike in 2003. If you look closely, you can see it in the movie Dogville (2003).
American History X (1998) was originally titled American History Twitter, but a fortune teller told them Elon Musk would rebrand it so they changed the title
Prisoners (2013) features the like of Wolverine, The Riddler, Scarecrow, Mysterio, War Machine and Amanda Waller. However, me and my 4 year old child realized it was NOT a Marvel/DC crossover.