Who is the comedian who plays the mystical character Rufus in the film "Bill & Ted's Excellent Adventure"?

In 1989, the comedian who gained popularity with a critics and movie fans when he was cast as Rufus, the time-travelling mentor of the title characters in "Bill & Ted's Excellent Adventure" was George Carlin. Also in the film sequel "Bill and Ted's Bogus Journey", he repeated his role as Rufus, an experienced and trusted adviser.

The film "Bill & Ted's Excellent Adventure" has two key protagonists. They are state of California high school underachievers Bill (Alex Winter) and Ted (Keanu Reeves). They face flunking out of school if they can't give a year-end history presentation and get passing grades. Using a time machine, they transport themselves back in time a few millennia. In the past, they enlist the help of Genghis Khan, Abraham Lincoln, Billy the Kid, and Socrates (among others). They even manage to talk to a couple of famous medieval females. Based on their adventures, they give a class presentation which is a 'funky' show-and-tell.