Funny or Guilty?

Just now, in school, we had double period chinese, and the teacher told us to do some exercises in the workbook.Ok, everything was ok...until the time we discuss the answers. HAlf way through discussing the answers, suddenly, MK used a deep voice(almost like mooing) to answer. He thought it was funny, my friends and I also think it's funny.But, the teacher went angry. She asked which cow mooed? MK did not confess. He even said,"Why you guys looking at me? Not me ah..." The teacher went more mad. MK still refuse to confess. Few seconds of silence, and he confessed. After some lecture from the teacher, she continued the class. Yet, MK still keeps saying why us guys keep staring at him when the teacher is questioing who did it. He even said I is trying to imitate a person's voice. Well, for me, I think it's quite pathetic... If you got the guts to do it, then you must got the guts to admit it.In some occasion, it is FUNNY to do things like that, but,hey!! We're discussing in class man!! His action is funny or guilty? YOU decide!