[MeechMunchie]

One of my designs was basically just a human with a giant barnacle on their face. That was terrifying.

I don't think the Barnacloid (or Cirripedians if you want to sound like a pretentious game dev) reproductive cycle would allow for mating with mammals.

They're hermaphroditic with a few male traits, and reproduction is a largely a gentlemanly business agreement. When he has set up a good life for himself and decides he wishes to start a family, he'll consult a close friend. The descision to mate is doubly important because fertilisation is mutual, so he'll have to make sure that his friend also wants children. After that, they'll just find a quiet corner to exchange sperm (the penis emerges from a small vent at the bottom of the shell, and releases the sperm into the frontal chest cavity), and spawning follows a couple of months later. While they will not raise the offspring as a couple, they will share a close bond and will consider it their duty to assist each other in family matters.

Too much?