Dr. Cruler & Dr. Fump

Dr. Cruller 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 monster 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, Cruller and Fump escaped with a prototype of Stark's repulsor cannon with it's own Arc Reactor.