I remember when they had Nerds cereal for a short time. One flavor on each side of the box. One time they had a mail in offer for a cereal bowl with a removable flood gate in the middle. You could put one color on each side, then open the flood gate - or whatever else you wanted to do with the weird bowl.
Trix was ok, never knew they had shapes other than colored balls. There was one cereal for a short time called "S'mores" that had square pieces and little marshmallows like you find in hot cocoa mix that was a favorite of mine. Nowadays, just eat Grapenuts...