You might also be familiar with Brad Carvey's younger brother, Dana.
[1] https://www.sandia.gov/xr/4th-annual-xr-conference/agenda/
Brad was, of course, the template for Garth. Dana first did the Garth voice as an impression of his brother.
That's it! I was struggling to remember his name. Just around the time of the Video Toaster, I was working at a small company in CT called Colorware. Tim Jenison wrote a Mac Paint clone for the Tandy/RS Color Computer II called CoCoMax. We bought the rights to it and paid him royalties on each sale. He made bank, IIRC! Soon after that, he created the Video Toaster and the rest is history.
I remember my co-worker saying that with the success of the Video Toaster, Tim had moved on from collecting cars to collecting airplanes.