Out here in the west, if we have a senior FA, they often know where the APU and pack switches are, and will tell you to turn on the AC, and know if you aren't telling the truth about it.

Ever have a stare down with a 40-year seniority FA? I've also seen them start the APU and turn on the packs...

It is possible to keep the guppy cool, but if you let it get warm and behind on the cooling, nearly impossible on the ground.