Not for pilot-episode-Phineas. Rewatch the pilot. Phineas has a glint in his eye. He wants to cause havoc. He wants to one up his sister for trying to tattle. He knows Isabella has a crush on him, he just has better things to do. Pilot Phineas is dangerously close to evil.
This is so funny to me because this is so out of character for them
#phineasandferb
