I can't recall what airline it was - AA / BA or AC, but I recall towards the end of the flight, a rather large bug (roach or beetle) crawled from the bulkhead past my seat towards the rear. It crawled slow enough that I could recognize it somewhat in the dark cabin, but fast enough that I couldn't react and squish it with my feet.

Gave me the heebie jeebies for sure, lol. Fortunately we landed shortly and I was glad to get off the plane quickly.

Pest control on airlines must be a full time job.