Richard Armitage
Armitage, more recently known as Thorin Oakenshield in the Hobbit movies, played Kruger, the HYDRA agent who tried and failed to steal a vial of super serum in Captain America: The First Avenger.
Kate Mara
Mara played a U.S Marshal in Iron Man 2, will be a hero in her own right as Sue Storm in Fantastic Four.
Gary Sinise
While he didn't have an on-screen role, Sinise narrates the Smithsonian's Steve Rogers retrospective featured in Captain America 2: The Winter Soldier.
Jenna Coleman
Way before she jumped in the TARDIS, Coleman was on Steve and Bucky's double date to the STark expo in Captain America: The First Avenger.
Ty Burrell
One year before Modern Family made Burrell a household name, he was Betty's psychologist boyfriend in The Incredible Hulk.
Natalie Dormer
Dormer, currently playing Margaery Tyrell on Game of Thrones, was Private Lorraine in Captain America: The First Avenger, also known as the lady who straight up makes out with Steve. Go Steve!
Joseph Gatt
Gatt is one of those actors who always plays "that guy" in "that thing" (recent credits include Game of Thrones, the Star Trek reboot and sequel, and True Detective), but you may have missed him as Grundroth in Thor!
Christopher Eccleston
Eccleston was barely recognizable as Malekith in Thor: The Dark World but sure enough, there he was.
Olivia Munn
Munn played Chess Roberts, a reporter at the Stark expo in Iron Man 2. She'll soon be back in the Marvelverse (sort of) as Psylocke in X-Men: Apocalypse.
Danny Pudi
It was a quick scene, but Community's Danny Pudi plays one of the IT guys in Captain America: The Winter Soldier.
Bingbing Fan
Superstar Fan only appeared a five-minute extra scene in the Chinese version of Iron Man 3. She plays the surgeon who finally removes the shrapnel from Tony Stark's body.
Nathan Fillion
Fillion, a sci-fi fan favorite, voiced one of the Kyln inmates in Guardians of the Galaxy. Yep, that's his character up there!