Back Alley Brawler, City of Heroes animations developer, combines awesome with oops:
When we were testing the invasions on the training room, I logged into Galaxy City while an invasion was going on, flagged the BABs trainer as invisible, stepped into his spot and made myself visible, and then joined in the fight against the Rikti.
After it was all over I went back to the trainer to make him visible again, but being invisible…I couldn’t find him to target him. He was completely invisible, even to me.
A couple of days later we got a bug report through QA about the Invasion causing trainers to disappear.