He and Peter Woodthorpe have both played Gollum twice. Theodore played the role in The Hobbit (1977), while Woodthorpe played him in The Lord of the Rings (1978). This incomplete adaptation sparked two other adaptations: the animated The Return of the King (1980), in which Theodore reprised the role; and the BBC radio production, in which Woodthorpe reprised the role. Theodore played the role opposite Orson Bean, who played Frodo, but had previously played Bilbo in The Hobbit. Woodthorpe played the role opposite Ian Holm, who played Frodo, and would go on to play Bilbo in Peter Jackson's films.

[from an interview done in 1998] I'm in perpetual pain. I have arthritis, you know and, uh, I don't want to really go into it. People are not interested in my woes. They say old people talk about nothing but what ails them, you know. I lost many friends by talking incessantly about my pain. They're not interested in my pain.