I know you are just trying to think like a crazy person but this really is a stretch even for two nut jobs (Casey & Kronk). I can see the conversation now:
RK: Hey, lady. What are you doing with that little girls body? She looks dead.
KC: I tell you what, keep your mouth shut and you will get a lot of money out of this. Tell anyone and my ex-cop, sexually abusive father will kill you.
RK: Do you have a plan?
KC: Do I have a plan? Puh-leeze! I am going to drive around with her body in the car for a few days until I can't stand the smell. Then, I will dump her in the woods, ditch the car, and party hardy until people finally notice she is missing. I'll show you the spot where I dump her and if you wait until a month after I am arrested, I am sure there will be reward money.
RK: Tell ya what, I will wait 6 months just to play it safe. After all, I'm sure none of the search crews will be able to find her.
KC: Great! Hey, by any chance do you have a duct tape fetish?
RK: Yeah, why do you ask?
KC: No reason!
RK: Ummm.......Ok? Who will you say did it when I discover the body?
KC: I am going to blame it all on my nanny.
RK: That seems plausible!
KC: Well, yeah, but the only problem is, I don't really have a nanny.
RK: Oh.......
KC: But don't worry, I will think up something while I spend the next 3 years in jail. Don't screw me with our plan or I will screw you.
RK: Okay. Good luck! See ya in court a few years from now.