The actor who has appeared in Doctor Who the most is Bernard Cribbins, who played Tom's grandfather, Wilfred Mott, in the show.
Cribbins appeared in Doctor Who for a total of 16 episodes across various seasons, starting with his first appearance in 2007.
He was a beloved character and his presence in the show was always a delight for fans.
While many other actors have appeared in multiple episodes, Bernard Cribbins holds the record for the most appearances in the show.