Welker's first on
camera film role was as a bar fight participant in Stan Dragoti’s 1972 film Dirty Little Billy. His next film role
was in The Trouble with Girls,
portraying a college kid from Rutgers University who befriends Elvis Presley. He later
co-starred with Don Knotts in
Universal's How to Frame a
Figg. Welker also appeared in two Disney films, The Computer Wore Tennis
Shoes, and Now You See Him, Now You
Don't.
His on camera
television appearances included roles in Love American
Style, The Partridge
Family, and The Don Knotts
Show. He played a prosecutor in highly acclaimed ABC special The Trial of
General Yamashita and as Captain Pace beside Richard Dreyfuss' Yossarian in Paramount television’s pilot, Catch-22. He also appeared on Laugh In, The Dean Martin Roast, The Mike Douglas Show, The Tonight Show,
Merv Griffin, The Smothers Brothers Show,
The Burns and Schreiber Comedy Hour, Laugh Trax, and as one of the
cast members in the 1985 special of That Was the Year That Was with
David Frost. In the latter
show, he appeared alongside Jim
Staahl and Howie
Mandel. Frank also played an on camera role of a voice actor on an episode
of Simon & Simon
and in the film The Informant as Matt Damon's father.