Has provided voices for eight of the original 14 Decepticons on The Transformers (1984) animated series: Megatron, Soundwave, Skywarp, Laserbeak, Rumble, Frenzy, Ravage and Buzzsaw. He voiced two of the original Autobots as well: Trailbreaker and Mirage, as well as one of the Dinobots (Sludge) that also appeared in the first season.
Has done every voicing of Fred Jones for all of the Scooby-Doo animated series with the sole exception of A Pup Named Scooby-Doo (1988). Even in parodies and cameos on different television series, he has always done this voice.
Has done voices for both the original Star Trek film series and the television series Star Trek: Voyager (1995).
In Tiny Toon Adventures (1990), he voiced Furrball, Gogo Dodo, Calamity Coyote, Little Beeper, Byron Basset, Uncle Stinky Pig, Henry Bear and Ralph the Guard who later appeared in Animaniacs (1993), where Frank not only voiced Ralph, but also voiced Thaddeus Plotz, Buttons, Runt, Flavio Hippo and Chicken Boo.
His broad spectrum of character voices, noises and other vocal effects that have appeared over the last 40 years in motion pictures, have vaulted him to number one on the "All Time Top 100 Stars at the Box office" list. The revenue of films he has participated in have generated over 12 billion dollars worldwide. His work in over 90 films has put him ahead of Eddie Murphy, Harrison Ford, Tom Hanks and Samuel L. Jackson.
Although he never met with the producers or the director Michael Bay, Bay felt his Welker's G1 Megatron voice did not fit the film and Bay's new interpretation. Ironically, he recreated the G1 voice for Transformers: The Game (2007) based on the movie, and was once again reunited with his old nemesis Optimus Prime played by Peter Cullen.
One of the most prolific voice actors of all time, he has been involved with some of the most popular and important animated series of all time as well, beginning with his role as level-headed leader Fred Jones on "Scooby-Doo", the evil Decepticon leader Megatron on The Transformers (1984) (among others), Dr. Ray Stantz on The Real Ghost Busters (1986), and a variety of supporting roles on G.I. Joe (1985), Tiny Toon Adventures (1990), Animaniacs (1993) and The Smurfs (1981).