Mattinson started at Disney, working in the studio mail room as a "traffic boy" in 1953 where among his duties, he would hand deliver weekly checks of $300 to Walt Disney for Walt's "walking around" money.
After a while, he was eventually promoted to be an animator in the animation department in the 1970s before becoming a story artist. During the 1980s, he directed and produced Mickey Mouse's comeback featurette Mickey's Christmas Carol and the full-length feature The Great Mouse Detective. Mattinson continued to work as a story an on features from the Disney Renaissance, such as Beauty and the Beast and The Lion King. His latest work was being head story artist for Winnie the Pooh.
In 2013, Mattinson celebrated 60 years with the Disney studio, and was honored with a surprise recognition by John Lasseter at the animation presentation at that year's D23 Expo. Recently, he has been trying to pitch a traditionally-animated feature starring Mickey Mouse.
In 2018, he became the longest serving Cast Member, of the Walt Disney Company.
|1955||Lady and the Tramp||Inbetweener (uncredited)|
|1973||Robin Hood||Character Animator|
|1974||Winnie the Pooh and Tigger Too!||Animator|
|1977||The Many Adventures of Winnie the Pooh||Animator|
|1977||The Rescuers||Title Artist|
|1981||The Fox and the Hound||Story|
|1983||Mickey's Christmas Carol||Story Adapted By/Producer/Director|
|1985||The Black Cauldron||Story|
|1986||The Great Mouse Detective||Story Adaptation/Producer/Co-director|
|1991||Beauty and the Beast||Story|
|1994||The Lion King||Story|
|1996||The Hunchback of Notre Dame||Story|
|2011||Winnie the Pooh||Senior Story Artist|
|2014||Big Hero 6||Story Artist|
|2016||Zootopia||Story Artist (uncredited)|