A couple of weeks ago my manager asked me to stay in the office for 3 hours more (after a full 8 hours there) because he had to go to a client and
1. I'm doing an interim + thesis for my graduation in that company so I'm not a real employee there
2. I did that project because it was slightly related to my thesis
3. Nobody else was available due to another project (he, the same manager, hasn't assigned the roles for weeks and now everybody has to work overtime because it's late)
4. I had an exam the following week
5. He should have gone after lunch and asked me to be available in that time frame but he disappeared and came back at the end of the day

I literally escaped with "I've an exam next week and I'm gonna miss the bus. Bye bye"