This broke my brain, I identified it as “The Mist” but I was 100% sure Mark Wahlberg was the main character so I was trying to work out what the joke was/why Wahlberg was replaced.

Guess I have my own Berenstein Bears thing going on.

you are confusing the Mist with The Happening. which starred Mark Wahlberg.
Mark Wahlberg playing a science teacher was the most unbelievable thing in The Happening.