While it is very well known that Casey Kasem retired from the role of voicing Shaggy in 2009, it is lesser known that Kasem also retired from his other famous role, as the host of American Top 40 at the same time.
Kasem had been doing AT40 since its original broadcast premiere on radio stations July 3, 1970, where the radio show aired live across 7 different stations. By the early 80's, that number jumped from a respectable 7 to a worldwide sensation of being aired live on over 1,000 radio stations in several countries at the same time. Due to contract concerns, Kasem signed off from American Top 40 silently without making any announcement to his fans, handing the role briefly over to Shadoe Stevens. Still having a passion for radio, Kasem decided to make his own independent radio countdown show entitled "Casey's Top 40." This caused American Top 40 a significant ratings drop, yet also cemented Casey's role as "the golden voice" of top 40 countdowns in radio history.
Due to Casey's phenomenal success and the signing off of his replacement Shadoe Stevens (leaving American Top 40 essentially hostless for a brief period of time), Kasem received a generous offer from iHeartRadio in 1998 to resume being the official host of AT40, in addition to hosting other alternative chart countdowns and shortened versions of the American Top 40 for them (such as American Top 10 and American Top 20). Kasem stayed in this role until 2004, when he voluntarily stepped down to pursue other projects, one of them being voicing Shaggy in "What's New Scooby-Doo" and the DTV movies. Because Kasem wanted to stay in his passion of radio, Kasem offered to continue hosting the American Top 10 and American Top 20, but offered the role to his friend and former AT40 guest host Ryan Seacrest, who still continues to host American Top 40 every Sunday to this date, in addition to his other radio show, On Air with Ryan Seacrest along with co-host Sisanie.
After Kasem's retirement, he was approached by several different radio outlets and was asked for the syndication rights to re-air old shows of the American Top 40. Kasem signed the legal contract to have his shows syndicated and re-aired in 2006. Due to the extreme popularity of Kasem's voice and countdown, the classic American Top 40 is still re-aired on radio stations around the world every Sunday (to keep with the spirit and tradition of Kasem's countdown, which also aired every Sunday morning).