Toad Core is a minor character that has only appeared in Portal M4R10 - If Mario was in... Portal. It is a space core with a Toad hat.
GLaDOS give him to Mario as a partner, but Mario gets annoyed with him and throws him into a pit of contaminated water.
When Mario is fighting GLaDOS, he sees Toad Core and uses him as a bomb.
He is most likely dead after GLaDOS explodes.