Donnie from The Wild Thornberrys was voiced by Flea from The Red Hot Chili Peppers.
Michael Peter Balzary got the nickname Flea from a joke he had with some of his high school friends. At some point they decided to call each other with a cartoon name, and finally "Flea" remained as the name by which all of his friends were calling him.
His friend from junior high, Keith Barry, who played saxophone with the Red Hot Chili Peppers during the Mother's Milk tour in 1989-1990, also got his nickname "Tree" the same way. Met Peppers pal Anthony Kiedis at Fairfax High School. When a kid, he played the trumpet and wanted to become a jazz trumpet player. He's lnown for his role as Needles in the Back to the Future sequels. He also voiced Donnie in The Wild Thornberrys on Nickelodean.