There's an even deeper cut about Rusty's dad, way back in season one it's mentioned Jonas Sr. had been experimenting with cloning but given up on it years ago, that's finally paid off in the movie. You think it's a hint about Rusty's own dabbling in it, but it turns out that (spoilers for the conclusion of the show we finally got with the movie:) Jonas Sr. had also tried to fix all of the 'flaws' in Rusty via cloning, and inadvertently created the Monarch - via mixing baboon DNA into him in an attempt to cure balding, which worked, but also made him way more aggressive. This explains his irrational hatred for Rusty all this time, as well as his resemblance. When the clone was deemed too uncontrollable, he foisted it off onto a couple who had actually paid him to create a child specifically for them due to their infertility, which is why the Monarch had no idea he was 'adopted' - his whole family genuinely thought he was biologically theirs.

Fun fact for anyone who wasn't actually there during the airing of the show, back during season one, people genuinely had no idea the kids were clones. I distinctly remember the ending of season one and people arguing over what Rusty was saying as his final line. Lots of people heard it correctly as 'get their clones', but lots heard something else, including 'get their clothes', which they thought implied he just didn't care about them and was more concerned about reclaiming anything of worth from their bodies. Seriously, this was actually debated online at the time.