Alphys is a short, round, yellow-green reptilian monster with a dinosaur-like appearance. She tends to carry a large purse equipped with several technological devices , and has three fingered hands. Under her neck is an electronic device which seems to work as some kind of vision enhancer or magnifying glass. Not much is known about her, even though she appears in several episodes.
Alphys is a nerdy, socially-awkward, and self-conscious monster who admires Undyne and spends time with her during the True Pacifist Route. She works as the Royal Scientist for King Asgore under both of their assistants, researching ways to pass through the barrier and find a new home for monsterkind.
Alphys is also the creator of Flowey, and it’s heavily implied that she created Mettaton as well. It is revealed in the True Pacifist Route that Alphys has developed feelings for Undyne, but her scientific experiments have trouble expressing them. In “Long Road Ahead” Alphys accidentally sends an email to Asgore saying that she is in love with him. Because of this, Alphys becomes very anxious about her apparent ‘love triangle’ with both Undyne and Asgore, believing Undyne will be angry at her for saying the wrong thing again. After the protagonist reaches New Home , it’s revealed that Alphys has hidden mechanisms in the walls that can activate new traps when certain steps are followed. Once she is paid with pictures of Toriel and Asgore kissing, Alphys becomes very depressed, even attempting to sell her soul in Snowdin Forest . When Undyne calls off her fight with the protagonist , Alphys leaves New Home through a secret door, saying that she’s gone to the True Lab to do more experiments.
She believes that the protagonist ‘s soul is a very powerful substance and wants it for herself, but her determination wanes after reading Asgore’s diary. When they finally meet in person, Alphys asks the protagonist to call her “Alphys” instead of “doctor” or “lady”. She refers to the protagonist as “that sweet, oblivious fool” and “adorable.” She seems ready to accept whatever the protagonist decides about freeing the monsters.