Heinz Doofenshmirtz

Heinz Doofenshmirtz is an evil scientist who owns Doofenshmirtz Evil Incorporated, mostly known for being Perry the Platypus's nemesis.

Phineas and Candace's biological father
Heinz Doofenshmirtz was most assumed in fanfiction to be Phineas and Candace's dad. It is unknown when and where this was first brought up, however on August 9th, 2011, Dan Povenmire confirmed that Dr. Doofenshmirtz is not Phineas's real father during the NY TimeTalks.

Supporting Evidence

 * Similarities between Heinz and Phineas:
 * Triangle heads
 * Hair sprouts
 * Mechanical ability
 * Behavior (especially during "Hail Doofania!")
 * Skinny
 * Similarities between Heinz and Candace:
 * Lactose intolerace
 * Insanity
 * Pointy head
 * Slouch
 * Large Neck
 * In the Star Wars Episode, Phineas and Candace's characters are somewhat like Luke and Leia, and Doofinshmirtz is styled similar to Darth Vader. In the Star Wars universe, Darth Vader is the father of Luke and Leia.

Opposing Evidence

 * Confirmed by Dan Povenmire that Dr. Doofenshmirtz is not Phineas's real father during the NY TimeTalks.
 * Heinz's bad date with Linda, causing him to never meet her again ("What Do It Do?")
 * In "A Real Boy", he does not (or is not aware that he has) have a son. "I would like a boy, in /addition/".

Fanfiction

 * A Boy's Search for Answers
 * Phineas' Other Family