If my Brother laser printer starts while I have the ceiling fan going on the same circuit, the breaker will trip. That's the only thing in my house that will do it. It must be a huge momentary current draw.
It's mostly the fuser that is sucking down all the power. In some models, it will flip on and off very quickly to provide a fast warm up (low thermal mass). You can often observe the impact of this in the lights flickering.
