Cornflakes are a type of breakfast cereal.
In 1991, while Vernon Dursley took them on the run from wizards, the Dursley family and Harry Potter ate stale cornflakes and cold tinned tomatoes. for breakfast while staying at the Railview Hotel.
In February 1994, Neville Longbottom was having cornflakes as part of his breakfast when he received a Howler from his grandmother. After he fled the Great Hall, Hedwig arrived with a letter for Harry and Ron, then helped herself to some of Neville's cornflakes.
There exists a spell that causes one's skin to look as though it is coated in cornflakes.
- Harry Potter and the Philosopher's Stone (First appearance)
- Harry Potter and the Prisoner of Azkaban