Dr. Long John

Dr. Long John is a character from Phineas and Ferb and is a minor antagonist in the first season of The Knights of the Multiverse. He is a "scientist" that works with the evil organization L.O.S.R..

Personality
As he isn't really a scientist, Dr. Long John acts like a typical pirate. He's loud, frequently violent, full of himself, and mostly spends his time looking for treasure on the open seas.

Pre-Series
As was typical of most of L.O.V.E.M.U.F.F.I.N.'s stranger ventures in its formation, Long John was hired by Dr. Heinz Doofenshmirtz when the group was being put together, mostly just 'cause he thought the group needed more diversity. After that, he didn't really... do anything scientific related. He mostly just served as a guard for other members when he wasn't "searching for treasure on the open seas", or whatever he called it.

Other L.O.S.R. Personel
The rest of L.O.S.R. have always seen the inclusion of Long John as one of Doofenshmirtz's dumber ideas, and view him as just one of the guys who're there.