Them is a group of three women who mostly appear together as a sort of Greek chorus. The tall stylish black woman is named Yemisi and has been employed by Yay as a personal shopper. The short white human with glasses is Willow Dragonfang and the AI is named Iris. They were roommates in college, and they live together currently.
They appear together several times. First, when Dale was wearing Emily's prototype Coffee of Doom uniform, then twice while Elliot has been having a moment with first Brun, then Clinton. Willow, Yemisi, and Iris have each gone on to appear by themselves.
Willow and Iris work at a lunch place that serves tacos and burritos. Iris "[doesn't] even like men", and she has also been seen getting a spray of a crossed out heart, but there has been no information about the sexuality of the other two. Jeph refers to them as Them in both the strip title of one of their appearances, and the comment below that strip.