Re: Unexpected fan favorites who take over the show?
Nobody has mentioned David Hewlett's Dr. Rodney MacKay on Stargate Atlantis. That role was originally written for an African American actor who would play an 'unflappable astro physicist' and they had trouble casting the part and at the last minute called in Hewlett to reprise Rodney. According to a Gateworld interview with Hewlett, he thought he was going to have more of a limited role following Weir around and giving status reports. He never expected all the screen time and guns. After the pilot episode they started changing the character to play towards Hewlett's strengths.
Give each other $10, put it on Underhill.