Inbitween is based off of stereotypical gay culture, with its resemblance to a unicorn and rainbow sunglasses, both of which are commonly associated with homosexuals. It being an equine with a male marking on its flank could be referencing the TV show My Little Pony. Its triangle shades may be a reference to Dirk Strider from the webcomic Homestuck, an openly gay character who likes horses, though this could be coincidental. The fact that it can possibly change genders upon evolution may be a reference to transgender people. Its bright blue shiny coloration resembles Rainbow Dash from the previously-mentioned My Little Pony.
Inbitween is a combination of in between (referring either to those questioning their sexuality or to transgenders who are in the middle of transitioning), and bi (as in bisexual). This is despite it losing the ability to learn Attract in the full release, and instead being able to learn the new Gay Agenda. (Though this is most likely just so Geigh couldn't have it.)
Geiponīis literally just gay pony, which further supports the idea of the species being entirely homosexual.