Upon returning from Stump Arena in Dimension X, the Teenage Mutant Ninja Turtles encounter a pair of aliens, one was the bat-like Wingnut, the other his partner Screwloose. The two were flying around Manhattan shattering skylights, believing that Krang was hiding inside one of the nearby buildings. The TMNT were soon attacked by Wingnut and Screwloose who destroyed the Turtle’s blimp. After a short fight, the TMNT subdued and tied up the duo, but quickly learned the only reason they attacked them was in belief that the Turtles were working for Krang who had committed genocide on their home-world, leaving Wingnut and Screwloose the last of their respective species, at this point they were abducted by Cudley the Cowlick who explained to the TMNT that he was going to take them to compete on Stump Asteroid.
The TMNT later reunited with the duo of Wingnut & Screwloose, when the Turtles, Cherubae, and the Intergalactic Wrestling Federation joined forces against the Foot Clan and Maligna. At first it seemed Wingnut would be of little help, and that he was completely uninterested in joining the fight against the Malignoids, especially after he and Screwloose flew away from the battle completely, but in fact it turned out Wingnut’s super hearing detected the voice of Krang, and he attacked him, Shredder, Bebop, and Rocksteady, preventing the Foot Clan from obtaining the mystical Turnstone.
Powers & Abilities
Wingnut is super-strong, he has demonstrated his raw physical power fighting Slash when he pulled a palm tree out of the ground and swung it like a club (though the use of a palm tree as a weapon just made the situation worse). Wingnut can not actually fly, his natural wings are deformed, and thus he requires metal glider wings to fly, but they were later broken in a fight with a giant snake, thus leaving Wingnut flightless near the end of his comic book life, He also possesses super-hearing.
Other Media
Teenage Mutant Ninja Turtles (1987)

Wingnut and Screwloose appeared in the series episode Zach and the Alien Invaders. Here they were invaders from the planet Flagenon who attempted to turn Earth’s children into mindless zombies. He was voiced by Rob Paulsen.
Teenage Mutant Ninja Turtles (2012)

In season 2’s episode The Mutation Situation, April O’Neil‘s father Kirby O’Neil winds up accidentally exposed to Mutagen and mutates into a bat-like creature that Michelangelo briefly nicknames “Wingnut.” Donatello finds this disrespectful however and Mikey then proceeds to call him “Kirby Bat.”