Idly speculating, but he probably had to teach them to walk after he took them out of the tubes . I bet it didn't take them too long though, they're such quick learners!Seeing them outside the tubes and blinking and being alive probably brought on an unexpected rush of dad feelings Gaster wasn't prepared for, not unlike when he saw them move for the first time . For those few moments, all he wanted to do was teach them things and see what they could do (as curious about them as they were about each other ). Then he caught himself and remembered what he was supposed to be doing and SHUT IT ALL DOWNmuch more subsceptible to such moments of weakness early onHe's always avoided touching them and it's not because he has issues with touch or anything, but because while he's worried that touching them will get them more attached to him, he's more worried that it'll make him more attached to them and those latent dad feelings may awaken once again. AND HE CAN'T LET THAT HAPPENThis doesn't line up exactly with established details in the main comics but WHATEVER IT'S CUTE. A bit of fluff to make up for how rough the last one was, haha.Edit - Check out Fiore!Sans's dub! (Spanish) Sans, Papyrus, Gaster (c) Undertale: another excuse for someone to pick sans up