What do you get when you cross a brown chicken and a brown cow? Brown chicken brown cow! (Picture someone saying it like "bow-chicka-bow-wow") In any case, that's the joke that Abbi wanted to share with her boyfriend for his birthday cake. I guess her boyfriend had never had a birthday cake (how sad, right?) and so she wanted to surprise him with this cake with one of their favorite inside jokes. We decided that it would be cute to have little hearts around the cake symbolizing the love between the chicken and the cow (although I'm not sure if they actually get together in the end of that joke).