Cinnamon Marshmallow Scooby-Doo! was the first breakfast cereal made by Kellogg's based on the Scooby-Doo franchise. It was sold from 2002 to 2008, and rebranded in 2013 as Scooby-Doo! cereal, likely for the Canadian market.
As part of this cereal's introduction, Kellogg's held an event in Branson, Missouri, called the "Kellogg's Scooby-Doo Cereal Sound-Alike Challenge". Participants were asked to do their best Scooby-Doo voice impersonation while eating a mouthful of the new cereal. Hundreds of people took part. The winner was Jason Merrick of Cabot, Arkansas, who won a year's supply of Cinnamon Marshmallow Scooby-Doo! cereal.
In a press release about that event, dated August 27, 2002, Kellogg's described the cereal:
"Now available at supermarket and grocery stores nationwide, new Kellogg's Cinnamon Marshmallow Scooby-Doo Cereal brings the fun of Scooby-Doo and all the gang, including Fred, Daphne, Velma and Shaggy, to breakfast tables nationwide. Fortified with 12 vitamins and minerals, the cereal features crispy, sweetened cinnamon-flavored multi-grain bone-shaped cereal with marshmallow bits shaped like Shaggy, the Mystery Machine and the ghost. The cereal also includes fun Scooby-Doo games on the back of the box."
- Cinnamon Marshmallow Scooby-Doo! at MrBreakfast.com