Board Thread:General Discussion/@comment-33255176-20171006013144/@comment-32182236-20171009222520

Asgore doesn't remember Gaster-He was forgotten. Sure, the Core still exists, but that doesn't change the fact that almost nobody remembers who Gaster was.

The only physical evidence of Gaster (and not just a previous Royal Scentist, I mean Gaster specifically) is Entry 17, but even that no longer exists-You can only find it by looing at the game's files. The last line:"WHAT DO YOU TWO THINK" more than likely refers to Sans and Alphys, his two partners. The only part of Gaster that wasn't forgotten was his final moment there-With Sans and Alphys witnessing it. The POSITION of that entry does not exist, but the entry itself remains, and so would memories of it.

Or, perhaps Alphys learned about Gaster from Sans:He may have not known Gaster had vanished, or did, but thought that only meant he died, but was still remembered, and attempted to speak about Gaster to a confused Alphys, which lead to him having to explain it all.. And that being how they met. Not really the best way to meet someone, and possibly a reason to get nervous trying to explain what happened, and, of course, Sans shrugging it off because he doesn't want Gaster to be brought up. One of the reasons why Alphys doesn't want to mention Gaster is because they all forgot about Gaster- that was in my original post!