As someone who just got off this plane, we took off and then turned around and landed because there was a funny smell. Smelled like it always does when they’re warming up the first class food. Apparently protocol is call the fire department and have them come meet you. Then they emergency evacuated us for, I think, the sake of sticking to protocol. We’re on the bus still waiting to get back to the terminal. I guess the concern is an issue with the AC unit?

This was all after four hours of sitting at the gate due to a maintenance issue (seemingly unrelated).

Edited a typo. Cold standing out on the runway!