Wally Cox will probaly always be known for his role as mild mannered teacher Mr. Peepers, but he also did well as the voice of Underdog, and was a regular on The Hollywood Squares. He also did dozens of TV series guest starring.
With his milquetoast voice, I think Wally Cox was stereotyped as the mild mannered nebbish, and he never really fullfilled his potential as an actor. Occasionally he would get a guest starring role where he would play against that image. My favorite as his appearance on The Odd Couple, in which he appeared in a scene with his former Mr. Peepers co-star, Tony Randall. In 'The Pen is Mightier than the Pencil', Felix is taking a creative writing course in which each student is reciting a poem of their own. Cox gets up and recites a poem that has decidedly erotic overtones. It is such a funny moment, because Cox is reciting it with that inimitable voice of his. For anyone who grew up with Underdog, it is certainly an off the wall scene. Sadly, when the show hit syndication, the Cox recitation is completely gone. The hope is, when that season is released on DVD, the scene will be on there. The the recent live action Underdog movie featured Jason Lee as the voice of Underdog, which isnt as bad as Bill Murray as Garfield, but certainly no one can truly replace Wally Cox in the role.