Simplify the following text for a Grade 15 native English-speaking person.
Original: He was one of the original three animators ( along with David Silverman and Bill Kopp ) on The Simpsons ' Tracey Ullman shorts and subsequently directed a number of The Simpsons episodes ( many of which had John Swartzwelder as an episode writer ) before becoming supervising director at King of the Hill .
Simplified: He was one of the original three animators ( along with David Silverman and Bill Kopp ) on The Simpsons ' Tracey Ullman shorts and subsequently directed a number of Simpsons episodes before becoming supervising director at King of the Hill for many years .