This may be a lie, but it's also a very cute prank as long as you have an opinion on pie. Pranks like this work best if the person either loves pie or hates pie. If the person has a fifty-fifty relationship with pie, they'll cut into this and just wonder, "what the hell is going on? Why would you ever do this?" I think that's just a cardboard box with frosting on it. Imagine if you tried to smash your face in it and just came into contact with hard cardboard and table.
Have you ever seen videos of people getting violent during birthday cake celebrations? People go absolutely crazy. They put their full body weight into the person's head as if that were necessary. I'm glad no one ever did anything like that to me.