From the Discord AMA with the Devs yesterday:
Multipart question: Who was the hardest character to design? Who was the hardest character to balance?
@Kaleidodemon Hardest character to design? Hmm. Probably Shayne & Aurox. It’s two characters that detach from one another and then re-attach. Our producer was pretty certain S&A was going to get cut for technical reasons. We’re delighted we got them in.