idiom. When there's not enough room in your heart for a load of lust, check your pants.
Real citation: "A Rhodes Scholar, lawyer and former Governor of Arkansas with lust in his pants and his Ivy league, ambitious wife come to Washington."
("Eight Years of Autopilot and Laissez-faire," http://www.angelfire.com/blog2/bigpicture/eya_19.html)
Made-up citation: "When female rats get jacked on coffee, it puts a little extra lust in their pants. I told you to stop giving Starbucks to the rats, Mom!"