Many details about Cosmo's father are not known clearly, only that he was turned into a fly by baby Cosmo when he got his first wand. His exact marital status with Mama Cosma is unknown, but seeing that Mama Cosma showed a hint of liking Big Daddy in the episode "Big Wanda", she is probably single; however, that particular relationship is never explored further. It is unknown if Papa Cosmo was ever turned back because he has not been seen in any other episode. However, it's likely he did because fairies can easily shape shift into other things and back to their original form. Since he was still a fairy, he could still be alive, considering that in "Fairly Odd Baby" it was stated by Wanda that fairies are immortal. It is unknown how his relationship is with his eldest son Schnozmo.
It is possible that he left Mama Cosma due to Cosmo's dimwitted behavior and incidents, such as sinking Atlantis nine times, destroying Pompeii, turning the high-tech utopia Xanadu into the heavily-polluted Pittsburgh, and repeatedly summoning a three-headed hydra named Snowball, causing the destruction of many things.
Much like his son Cosmo, Papa Cosmo has yellow green eyes and slightly longer green hair. He wears a pair of reading glasses as well as a green jacket with a white shirt and a black tie, paired with some black pants. He also talks in a deeper and more mature voice than Cosmo. After Cosmo gets his first wand, he turns his father into a green fly with large black compound eyes.
He is seen in the episode, "This Is Your Wish". During a flashback to when baby Cosmo is getting his first wand, Papa Cosmo tells Cosmo to fly to him. Unfortunately, Cosmo immediately turns his father into a fly who buzzes away, never to be seen again.