That was the wrong way, indeed.
years from now, Lyman asked Jon the same question, but with a cat (14 August 1978 Garfield strip)
It means You ruffled their feathers, or in this case, their fur.
Fur crying out loud, CB!
Snoopy’s having a tough week.
She makes my hair stand on end too.
Snoopy can use Charlie Brown’s line: “Why is everybody always picking onme?”