He wasn't even serious in the beginning of his strop, because he was smiling when he said to Tom that he's in the middle of a strop and Tom is ruining it for him. After that he got into proper mood, but it was excellent when that song started and the viewer could see the smile and the fingers from under the covers. It was funny. I have to say, that if I was in the house, I wouldn't want to share all my good moments with other housemates either.
