"Phineas Flynn" is the Lost in Danville Dimension counterpart to Phineas Flynn. He is identical to his first-dimension counterpart in appearance except having an extra white stripe on his shirt.
History
He, along with along with the Ferb, Baljeet, Buford and Isabella from the dimension tried to open the mysterious capsule, only to discover too late that it was used to protect Danville from a black hole