Hi Chidoriashi, thanks for your reply. Sorry, I don't understand this use of the passive. In English, the obvious (though it seems incorrect) translation would be 先生が教室に入ってこられた = "the teacher came into the classroom". There is no passive sense here that I can see.
LATER EDIT: Oh, unless it means that the students "suffered" the teacher's coming into the room??
Yes, 食べたピザ makes sense to me, but お世話になったお礼 doesn't.
食べたピザ = the pizza that (I) ate
お世話になったお礼 = (my) gratitude that ??? what ???
I don't understand how it works.
What form of 眠る? I was trying to make this verb work, but I don't understand what form of the verb it is. Passive seems not to make sense, and it's not the potential form, is it?