19 MCU Actors Who Were Also In LOST
2. Titus Welliver
On Lost: Welliver appeared in the show's fifth and sixth seasons as Jacob's brother, the Man in Black, whose desperation to leave the island over two thousand years before the crash of Oceanic 815 lead him down a path that resulted in his becoming the smoke monster.
Though a number of actors portrayed the character - like Terry O'Quinn in John Locke form - Welliver still showed up in the monster's original form in Jacob's flashbacks in "The Incident" and Richard's in "Ab Aeterno."
In the MCU: He made his MCU debut in the One-Shot "Item 47" as S.H.I.E.L.D. agent Felix Blake, a role he returned to for several episodes of Agents of S.H.I.E.L.D.'s first season before the character was brutally injured by Deathlok. He returned briefly in season three as the leader of the Watchdogs, but hasn't been seen since.