The eternal struggle of finding something funny and pithy but not in some way problematic to calligraphy. Where's the repository of "good quotes from people who don't suck"?
This sort of need usually finds me digging around in my clown wisdom archive. While the words stored there don't all come from untarnished origins, they were (but for a few exceptions) typically well intentioned.
Happy to hit the randomizer a few times for you if you need/want.