Phineas is an anthropomorphic fox and one of Varian's assistants. His fur is all black with spiky bangs and green eyes. He wears a black outfit, brown bandana, dark red boots, and gray gloves. He also wears a beige utility belt and goggles he wears around his neck along with a short necklace with a small fox fang tied at the end. He uses dual katanas as his weapons of choice.

Phineas makes his debut in the middle of season 3 where he is first seen helping his three comrades in creating a special robot dragon with amber breathing abilities which could bring protection and wealth for the valley. Phineas is highly intelligent and takes pride and caution in his work. Unlike his comrades, Phineas believes in magic but doesn't talk about it much. Regarding his social life, Phineas only seems to interact with his team. He does occasionally speak with other heroes but it's not common. He is quite shy and affable. He is the son of infamous pirate Black Tail.

Phineas and Varian are good friends and are normally seen standing side by side with each other's opinions. The young alchemist mentions he and Phineas met when he and his friends rescued the fox, Killian, Persephone, Teivel, Scooter, Ranger, Casta, and Antigone after the eight latters were captured by scientists for animal testing. Phineas seems to bear the most similarities to his leader than anyone of his teammates. When Varian goes away in the end of season 2 due to him turning evil, Phineas becomes devastated. He is overjoyed when his friend returns and the two share a tearful reunion.

Phineas is good friends with Killian with the latter mainly seen as the former's target for pranks.

Phineas is good friends with Antigone and is shown to have a small crush on her.

 Scooter and Phineas are close friends and seem to have a similar relationship to Rapunzel and Cassandra.

 Persephone and Phineas and share similar relationship to Eugene and Lance. They both enjoy creating mischief. 

Phineas loves and is protective of his little cousin Ranger.

Phineas likes Casta but the two are snarky to each other.

Teivel and Phineas are on good terms.

He holds great respect for Rapunzel and the rest of her gang, usually addressing her as "My lady."

Trivia:

Phineas is named after PT Barnum due to his love for odd things and circuses.

Phineas is shown eating small fruits and veggies, he is even seen faint when he sees meat, implying he's a vegetarian. 

Phineas and Varian share similar personalities and the same voice actor. 

In his debut, Phineas and his comrades were surprise characters for they just popped up from nowhere and they seem to already know the valley.

The fox fang on Phineas's necklace is never addressed but the fox looks at it when his father is mentioned, implying the fang belonged to him.

He mentions his unnamed mother three times during the show.

Phineas, Killian, Casta, Teivel, Persephone, Scooter, Ranger, and Antigone are the only anthropomorphic animals in Corona, a hint towards their capture.

He also mentions having a brother named Smokey and a cousin named Ash who helped Black Tail with his crimes.