But let's get back to his bread and butter - the cartoons! My first real experience with him, at least where I knew his name, was Megatron. That deep gravelly voice fit the Decepticon leader so well and I was floored when I found out he also supplied Soundwave's highly-synthesized monotone delivery (same for Peter Cullen delivering Optimus Prime and Ironhide's voices). Imagine my surprise when I read that Frank Welker had provided almost a dozen more voices in just that one cartoon.
While the Beast Wars cartoons and the Unicron Trilogy had different voice actors, Frank Welker began supplying the voice again in the Prime series and Devastation video game, his voice having grown a little deeper and more gravelly with age, though it still fit the roles perfectly. He's even returned to his role of Galvatron in the most recent Transformers movie. In the meantime, all of Megatron and Soundwave's appearances in Adult Swim's Robot Chicken came from the original source as well (same goes for his Dr. Claw).
Another life-long role for him is Fred Jones from Scooby-Doo. Throughout every incarnation of the cartoon (practically equaling the various Transformers series that have come and gone), Frank Welker provided Fred's voice in all but one. That's at least 15 different cartoons over the course of more than 40 years! Not to mention after the passing of Don Messick, he took over the role of Scooby Doo as well.
To go over Mr. Welker's whole career or filmography would be a daunting task, but as far as Transformers goes, this guy is a legend. As great as David Kaye or Corey Burton have been in their respective series, Frank Welker still stands above them. And let's not get started on how much better he would have been in the role than Hugo Weaving in the first three movies.