Calvin and Hobbes by Bill Watterson for February 21, 1987
Calvin: For the next 60 seconds, I will conduct a test of my emergency broadcast equipment. AAAAAAAAAAAUUUUUUGGGGGGHHHHH! Had this been an real emergency, the scream you just heard would have been followed by lots more just like it. This concludes my... Oh, someday when the house caves in, she'll thank me. Mark my words.