From the Grayskull Wiki:
"Meteorbs were originally a Japanese toyline of transforming eggs from Bandai called Tamagoras (タマゴラス) and were released in the USA by Mattel as part of the Masters of the Universe toyline."
I've been looking for one of these all year, trying to indulge some childhood nostalgia. As a kid I had Dinosorb, who turned into a dinosaur and Tuskor, the wooly mamoth. Then today a friend of mine gave me his old Transformers from the garage he was cleaning out and in the middle of it I found this guy!