There's a lot of cereal eating in this movie

I believe there's 4 times that cereal is being eaten. Young Peggy is eating it as she watches her dad read the newspaper about something violent.

De Niro eats it twice by himself while something bad is being reported on the TV (once while grown-up Peggy is staring at him).

And then at the end, Pesci and De Niro are eating cereal together ("Corn Flakes or Total?").

I think we can safely conclude that, in this film, cereal = murder