Board Thread:General Discussion/@comment-31540897-20170722153802/@comment-26678143-20170723232017

Well, now we know a LOT more thanks to Gaster's Tarot Card. It has MysteryMans sprite, proving hes Gaster. As well as a bone and a Gaster Blaster, meaning he probably is somewhat a skeleton. Also, it also seems to confirm that he created the CORE(even if we already knew that.)

And since the Card itself was approved by Toby Fox himself, a lot of the speculations were canon.