Lore time! Daisy is the name of the rabbit that Doomguy had and in fact because the demons killed said rabbit he kind of went off the deep end... Never mess with a guys rabbit. So, in my headcanon the Doomguy himself during a nice stroll through hell found her soul and brought her back to the labs in hopes of using futurustic healing tech to make a new body for her. It worked but it was only built for humans, resulting in Daisy the Doombunny.
I don't know if you ever saw it, but this amazing picture reminds me of Tom's (Twokinds) sketch of Doom and Daisy in an anthro form. I love her care free face while comitting genocide in hell.
