Wow! That might chafe in the tiny car!
I don't know how this internet chestnut passed me by, but it's apparently been circulating on the internet since 2001. The email that's been circulating tells you about a class of grade school children got to paint these pretty clown planters, then the teacher had them plant cactus seeds in them. When the cactus plants "came up", the teacher realized her folly, replaced the cacti with ivy, and the kids got to take them home. Sadly, it's just another internet flight of fancy. I think that just about anybody worth their flea market salt has come across these at some point. It doesn't make them less funny, though.
LINK thanks, Mary!