as a kid, I remember telling "knock knock" jokes and, at the time, thinking they were absolutely hilarious.
Orange you glad I didn't say banana?
I was never very good at telling jokes, though. I would either be laughing uncontrollably before I could ever make it to the punch line, or else, after telling a joke, I would right away try to explain it: "orange you glad, as in aren't you glad... haha, get it?" and then, whoever I was telling the joke to would look at me like I had suddenly grown another head and say, "of course I GET it, you moron. you don't need to explain it." oh, sorry, heh. eventually, I just quit telling jokes altogether.
anyway, this chalkboard speech bubble made for a fun way to relate an age-old "knock knock" joke. plus, by not having to talk, you don't have to worry about sounding like a fool. instead, you'll just look like one.
boo who, as in boo hoo I'm crying... haha, get it?