How I would fix Yang 3 in 2D
Also I know I'm writing this about 15 years after the fact and also, I know I don't have any sort of studio pressure so take this with a grain of salt lol ~
First - I would remove the Yin/Yang father/daughter dynamic and instead have them be a married couple. I would have them both be highly intelligent but Yang is either infertile or has a miscarriage and sort of goes off the rails and the two of them become convinced, somehow, that Shawn is actually their son.
I would keep pretty much everything the same in the first two installments, but in the third, I think they want to teach Shawn a lesson, or try to get him to succumb to their delusions and believe that he is the missing piece of their family. Meaning, they need to strip him of his other relationships/connections, to depend solely on him (again, working with fictional serial killer logic).
I would have the final installment be a 2-parter, and the first part should feel like Infinity War where everything goes wrong. It should start with Shawn and Henry getting in a big fight (ideally about Shawn's mom) and they're not saying anything to each other. His mom is in town. There's a suspicious murder either related to their previous case or a separate instance -- like in the first two episodes -- and Shawn realizes what is happening too late. Bam! His parents, taken!
We learn Yang has just escaped or been transferred and released is basically free. Shawn, Yin and Yang do their little dance and it should be a combination of the riddles from the first two installments as Shawn gets more and more aggravated.
Eventually, Shawn leads Juliet and Gus to a location (specifics are up to the people idc) and they, too, get kidnapped. So now it's just Shawn and Lassie (Shassie Stans, rise up) and that's how we end episode 1.
Episode 2 opens with Shawn in a disastrous way and Lassie is trying to help him and actually comes to see him a bit deeper, he starts to realize there's maybe a little method to his madness. Shawn realizes he's being set up by the Yin/Yang duo to have to choose who to save between the four people he cares about most in the world.
Alternatively - Yin/Yang could kidnap Henry and Gus and set Shawn up to lose one of his two anchors/the people who know he's not psychic.
It should be a back and forth, and then the episode should take one of three paths.
One - he's able to rescue his parents and Juliet, but nearly loses Gus and they are still able to have their moment about Gus saying he doesn't regret anything
Two - he saves everyone but his mother and she is killed (full circle with Yang kidnapping her in the first episode) this would hammer home the severity of the threat - if they choose to kill her I would have it happen at the end of episode 1 so there would be enough fallout time -- would also be fun to see Shawn go full-feral
Three - in order to save Juliet or Gus, he has to admit that he's not psychic -- I think this would be a very interesting path because he doesn't really admit it to anyone in the show, even those that figure it out. It would also really showcase what he values more than the lie he's built his life around.
Depending on the path chosen, that would influence the outcome of the trilogy and I think give a little bit more emotional connection to the Yin/Yang duo, and make it a little more satisfying if Shawn was able to actually outsmart them himself rather than relying on deus ex machina (a little) of Yang to rescue him.
I also think this version of the episode would amp up the stakes as they did for season 3 and 4 and keep the character drama and allow for more riddle solving. For me, the excitement of the episodes is seeing the characters in peril and watching Shawn be pushed to his limit, which I think any of those three scenarios would set him up for in a way that's a bit more satisfying than Yang being in the right place at the right time and human-lie-detectors Shawn and Henry Spencer getting duped.
