Board Thread:Questions and Answers/@comment-28292244-20160424121523/@comment-27701762-20160424183552

Sans (and presumably Papyrus, given a piece of dialogue added in the patch) have a special move called the "Gaster Blaster." If you've done/seen the Sans fight, it's those weird faces that shoot lasers. The name certainly suggests some connection, but what that connection is is entirely up in the air.

Since monsters innately have access to magic, the bulk of what Sans does would probably be the result of him simply being a monster. So the various bones he throws at you during his fight would not be a result of Gaster "giving" Sans magical attacks.