Charlie Brown

During Donna Noble's brief transformation into a half-Time Lord, as her mind began to overload, she confused Charlie Chaplin with Charlie Brown immediately after suggesting that she and the Tenth Doctor go meet Chaplin. She immediately corrected herself, noting that this was not a feasible idea because Charlie Brown "was fiction". (TV: Journey's End)

Behind the scenes
Charlie Brown, the main protagonist of Peanuts comic strips, was referenced in the comic story The Glorious Dead where one of the Doctor's counterparts from parallel universes, Theta Stigma, resembles Charlie (while the Rani resembled ).