These are the so-called "Gaster`s followers" and their prototypes. I'll explain now. Several scientists and his proxies work together with him: Kroffer, Oaket and Frass.

Earlier, when Gaster was part of the Shapeshifters community, his comrades were Xoran, Fleom and Laimer.

But when Gaster adopted Alphys, he left the community, cutting off any ties with them. For them, the worst thing was that a Shapeshifters uprising was impossible without Gaster's magic and mind. Therefore, after some time, they decided to bring him back by force, by killing Alphys. They take the distorted form of three other scientists, trying to get closer to the Gaster and his daughter.

Thus, it turns out that the three scientists and the "Gaster`s followers" are completely different monsters.