Hi I'm new here but when I saw this I just had to reply. I have so many good ideas for "Psych" some of which are crossover ideas for "Monk" as well but I'll post them here anyways.
PSYCH
1.) My first idea is to bring Mira back from "There's Something About Mira" (Season 2). Remember how at the end they kind of left it open so that she could come back? Well, you have Shawn and Gus think that they've won a cruise on The Sun Princess. I say The Sun Princess because that is where they filmed "The Love Boat: The New Wave" and as soon as he sets foot on the ship, he breaks out into "The Love Boat" theme. A murder happens on the ship and they solve it. At the end however, we find out the Mira went on the same cruise and that she was the one who paid for their trip. She also says that she tore up the divorce papers so technically she's still married to Gus!
2.) My second idea is to have a murder happen in or around a preschool. I know that sounds mean but the twist is that everyone has to go undercover at the preschool. Jules an Gus could be something like receptionists, asking the parents who bring their children in some questions about what went on. Chif Vic could be a Program Director, asking the actual Program Director the same questions. Which leaves Lassie and Shawn. They would not only be teachers but they would be teachers in the same classroom! Can you imagine them in a setting like that! Lassie wouldn't be too thrilled to be with kids and Shawn would be way too laid back with them, hence chaos!
3.) My third idea can either be one episode or can be an idea for an entire season. My idea is to have something happen to Chief Vic's husband and because she's too close to the case, she has to step aside. Lassie, being the second in command, now becomes the Interim Chief and Jules takes over Lassie's job. As you know, Lassie would rarely hire Shawn to work on a case, so he hires Henry to work as a consultant. Jules, as you know, would go behind his back and hire Shawn. As the case gets solved, Henry would have to ask Chief Vic some questions. Henry, we know has also been asking Shawn to help him find a significant other for quite some time now (since Season 2 I think). At the end of the first episode, we find out that he and the Chief are dating!! Lassie, with a look of horror on his face, realizes that the grass isn't always greener on the other side and wants Chief Vic to come back. Shawn would have a look of disgust on his face because he doesn't want them to date because he works with the Chief so now he and Lassie have to work together to break them up!!!
4.) I think someone already said this a while ago on another thread but I'll say it again here because I think it's a good idea. You could have Shawn and Gus each take a Lie Dector test. You have Gus tell the truth and have it say that he's lying. However, when Shawn takes the test and lies through his teeth, it says that he's telling the truth!!!
CROSSOVER IDEAS:
The only idea that has to remain constant in all these ideas is that you have both departments compare notes and find out who has the tougher job, particularly Natalie and Gus!
1.) Since just about every job profession has a convention you could have them go to a Police Convention and have a murder happen there. Now the departments have to work together to solve the case.
2.) Since both shows take place about 400 miles apart, you could have them be on a murder mystery train only instead of the murder being staged, someone actually does get murdered!
3.) For those of you who don't know, Monk's wife Trudy, was murdered via car bomb. The person who built the bomb was hired by a six fingered man. You could have Monk get a lead that leads him to Santa Barbara (sp!) where a simliar murder happens. Now here is where the writers would have some freedom: you could have the murderer of the crime in Santa Barbara be the same person who murdered Trudy or you can have it be a completely different person.
I know that's a lot but I've had a lot of time to think!!!!!

What does everyone else think?