A trans-Atlantic derogative of indeterminate origin, generally used to berate someone who is deemed to be inferior. Usage is widely believed to date back to World War II, where it was a popular ethnophaulism among the American forces, used as a slang term for recently deceased members of the Axis Powers, particularly Japan.
"You've broken the chain on my favourite bicycle you toasted raccoon! I'm going to muck your face to shreds for this!"
"I shot down several Jappo's last night, most of them ejected but I'm pretty certain that at least one of them was toasted raccoon, his parachute didn't open, haha!"