Dum Dum Dugan

Timothy "Dum Dum" Dugan is the bowler-hatted Howling Commando who fights alongside Captain America from the rescue at Azzano to the end of the war. He stays close to the people Steve left behind: he joins Peggy Carter on a mission into the Soviet Union in Agent Carter, and he's the one lounging by the pool with Howard Stark at the end of the Agent Carter One-Shot.

First turns up in Captain America: The First Avenger.