For anyone who was wondering about this picture, here’s something of an explanation:
This is a SUPER self-indulgent AU in which Flowey, during a post-pacifist timeline, decides to create another vessel so he can have someone with him in the underground. Using Alphys’ notes in her lab, he figures out how to turn an echo flower into a vessel he can bring to life with Determination.
And Flowey names them Echo, because like his father, he is an unoriginal goober.
This is probably one of my favourite post pacifist interpretations now.