Carmichael. Charles Carmichael.
Charles Carmichael is Chuck's favored pseudonym for use during spy work. He often uses the alias in undercover operations, and it is the subject of much humor between himself, Sarah and Casey.
The alias is often used in assignments where Chuck is disguised as a billionaire in software. Chuck originally envisioned Charles Carmichael as everything he himself wished to be, before his explusion from Stanford University in 2003 crushed those dreams.
From his style of introduction onwards, Carmichael is clearly an 'homage' to James Bond.
Coming to the final season of Chuck, it is shown that Chuck and Sarah now own a freelance spy firm known as Carmichael Industries because they were fired by the CIA. Both of them currently go by the surname of Carmichael as part of their alias when managing the organization, and it is perhaps part of their new selves.
See Also Edit
 - Season 1, Episode 3 - Chuck Versus the Tango