The gang's break up in the 2002 film, particularly Shaggy and Scooby. Fred, Velma and Daphne argue and decide to quit the gang, and all Shaggy can do is to quietly protest, to no avail. And then Scooby asks "Do I quit?", with Shaggy responding "No Scoob, Friends don't quit."
The 2014 death of Shaggys original voice actor, Casey Kasem.
The 1997 death of Scoobys original VA, Don Messick.
The 1999 death of Mary Kay Bergman.
The worst part? She took her own life.
Bill Lutz, the writer of SDWAY Season 1, died in 1973. He never got to see how wonderful people thought his work was.
The 2017 death of Daphnes second VA, Heather North.
Their creators (William Hanna and Joseph Barbara) deaths in 2001 and 2006, respectively.