It's an all-star cupcake showdown as celebrities Greer Grammar, Maria Menounos, AJ Michalka and Tamera Mowry battle it out to prove that their cupcakes reign supreme. These four stars will have to shine bright to have their cupcakes featured at a galactic blowout celebrating the end of astronaut Scott Kelly's one-year mission in orbit, the longest in history! Bobak Ferdowski from NASA's Jet Propulsion Laboratory is on hand to choose which celebrity wins bragging rights and a donation to their charity of choice. (thetvdb.com)