Dumbest comment I've gotten was at a Toyota dealer. Friend wanted to stop by to check out the FR-S (killing time), and the general manager asks if we came in the Miata.

Only other car out front was a 370Z. Yeah sure, "20 years in the business" and you can't tell the difference between a Miata and a Boxster? Or was it some sort of slight since two guys came up in a roadster?
Funniest was when I took dad's 964 out. It's a '91 C2 Targa in Guards Red. At a stoplight, I hear a little voice "Mommy, look at that ugly car! Isn't that red car ugly, mommy?" I was in the only red car at the light. I glanced over at the mother, she looked embarrassed.