Greg is a minor character in Sailor Moon. He is the third rainbow crystal carrier, and therefore the spirit of one of the Seven Shadows, Bumboo, resides inside him. He is also friends with Amy. He has some sort of psychic power, as he knew Amy was Sailor Mercury, and also knew that Zoycite was going to turn him into a monster. Even when she did (taking his yellow crystal in the process), he still retained some of his human mind, as he attacked Zoycite before she completely turned him into a monster. Eventually Sailor Moon healed him with Moon Healing Activation. He then moved somewhere because of his father's work.
He later returned in Episode 37, Tuxedo Unmasked. The brainwashed Prince Darien was attempting to recapture him, as well as the other crystal carriers, in an attempt to use the powers of Seven Shadows (who were killed when the crystal carriers were healed, yet their power remained) to summon an invincible shadow. He eventually trapped him inside a crystal, but was later released when the crystal was destroyed.