The CORE never blew up here and Alphys isn't a jerk who steals research or schemes against colleagues. Everyone except Sans and Flowey is different. To this world you are dead, you don't exist at all. How is being dead so nice? Enlighten me! AH! Gaster, you're cracking!?! 

Gaster wait..! Magic Anon, Gaster can be seen by and interact with his brothers for 10 asks. Gaster... They would just want to see you in general.. They have been sad without you.. Especially Sans. Even if you couldn't stay.. Wouldn't you want to talk to them again? Wouldn't you want to hug your brothers again? And maybe you could have a proper goodbye? If there is one thing you would like to say to your brother and Flowey, what would it be?

I think they both need some words of encouragement, something that they know would have come from you. I'll be sure to tell them. Is that all you want to say? Take it from me, sometimes you regret what you didn't say.