Background

Alphys was born in the Underground, much like many other monsters born after the war, to an engineer who worked at Steamworks prior to getting shut down. While born male, Alphys transitioned by the time she was in college. As a child, Alphys parents had high expectation for her.  In her free time, Alphys would often venture to the Garbage Dump where she was first introduced to human anime. Her parents would openly express their disappointment towards Alphys' interests, which lowered her self-esteem.

While attending college, Alphys met Sans, who became a good friend to her. Around this time, Alphys also met Mettaton after responding to an advertisement for a "human fan club". Following her graduation, she and Sans began to work under W.D. Gaster for a brief time before Gaster fell into the void. Following this, Sans ultimately quits and moves to Snowdin with Papyrus.

In an attempt to impress Asgore as well as help Mettaton become a star, Alphys created a robot body for Mettaton and presented it to Asgore as a "human eradication robot". It works and Alphys is made King Asgore's royal scientist. At Asgore's request, Alphys begins SOUL research in order to break the barrier.

Alphys sent letters out to everywhere in the Underground, asking for monsters that have "fallen down" Using a determination extraction machine, Alphys is able to extract determination from the already captured humans. With this determination, she injected it into both the fallen down monsters as well as a golden flower. With no results on obtaining monster SOULs, she goes ahead and notifies the families. However, the determination-injected monsters end up becoming amalgalmates and the determination-injected flower vanished. Out of fear of the reactions from the other monsters, Alphys shuts herself off from the rest of the Underground.