Dr. Cruler and Dr. Fump are a duo of mask-wearing scientists working for HYDRA, that appeared the Marvel Heroes United series.

Iron Man and Hulk

They created an Arc Reactor that powers on gamma radiation. So they hired Abomination to bring them the Hulk, and then tricked him to used both gamma monsters to power the reactor. But their experiment failed, and they accidentally created the energy eating villain, Zzzax.

Iron Man and Captain America

HYDRA infiltrated Tony Stark's flying fortress, led by Taskmaster. While Captain America and Iron Man were busy fighting off the soldiers, Cruler and Fump stole a prototype of Stark's repulsor cannon with it's own Arc Reactor. When Taskmaster captured Captain America, not only did the Red Skull had Cruler and Fump take the Captain's blood with the Super Soldier Serum, they also download his skills and dedication to put into the minds of the Skull's new army of Super Soldiers. When they were done, they uploaded the Skull's influence into Cap's mind. Multiple HYDRA scientists, dressed like them, were creating the Skull's army of Übermensch.