2. Peter Weller
Some may have recognised the name in the opening credits, but many may not have recognised the aging face of the man who played Christopher Henderson in 24's fifth season. It belongs to Peter Weller, best known as the original portrayer of RoboCop, the 80s action film that has already been discussed briefly during Kurtwood Smith's earlier entry on this list. Perhaps the most notable of all of the roles featured on this list, Henderson is introduced as a former director of CTU who was instrumental in recruiting Jack Bauer to the organisation. Never one to let a friendship get in the way of his duty, however (just ask Curtis Manning), Bauer discovered incriminating evidence against his mentor proving his involvement in the sale of classified information, which led to the termination of his employment. He returns to his protégé's life as part of season five's plot, as part of the company responsible for manufacturing the nerve gas that is being used on American soil. Complicit in this (along with the likes of President Charles Logan), he meets his end after several confrontations with said protégé.
1. John McCain
Despite incorporating a host of politically sensitive subjects into its storylines, 24 is a favourite of many politicians, including current President Barack Obama (or Barraco Barner, if an airhead from Blackpool that has gone viral is to believed...), who should be commended for his taste in television given that he also counts Game Of Thrones, Homeland, House Of Cards, Mad Men, Downton Abbey, Breaking Bad and The Wire amongst his favourite shows. In the 2008 Presidential election, the Democratic Obama ran against the Republican John McCain, who ultimately came up short in a close race. Despite their contrasting political ideologies, however, the two contenders are united in their appreciation of Jack Bauer's heroics. Unlike the man who beat him, McCain acted on his appreciation to secure a walk-on role on the show, appearing in the background handing a file to Audrey Raines in season 5.