The "Goozim" is the 2nd Dimension counterpart of the Goozim from the 1st Dimension. This one is used by Heinz Doofenshmirtz to play his favorite game: Poke the Goozim with a stick.
This Goozim was captured at some point by the Norm Bots before the events of the movie, and was sealed inside a cage so Doofenshmirtz could use him for his game, and also to give doom to his prisoners.
This was seen in action when the 1st Dimension Phineas, Ferb, Candace, Perry and Doofenshmirtz were sent to get their doom. He managed to get out of his cage and pursued them, including going through the portal they used to escape.
When they got there, the Goozim arrived and it was revealed that he had lost most of his fur, including his limbs. Noticing this, the Goozim started to whine as he slipped away, never seen again after that.
The Goozim, physically, is identical to his 1st Dimension counterpart. However, after falling through the portal that the 1st Dimension prisoners went through, as indicated above, his fur and limbs were shaved off, leaving him with a cylindrical body.