To plot or scheme in a decidedly rat-like manner, esp. when formulating an agenda for the acquisition of cheese and/or shiny objects.
Just look at those two nefarious-looking furry midgets in the corner there... they are clearly rataplanning something.
The planning stage for an event that occurs after the pre-plan but before the actual preparation for the event.
"I don't want to shower and get ready yet, I have like three more hours to rataplan before I have to do any of that."