The details of the rat caper are here: Ryan Conklin And Girls.
As fun as it was watching Devyn wig out, Ryan was even more gleeful when he got a similar reaction from Sarah after he decided on his own to give her the same treatment. Sarah annoyed the hell out of Ryan and making her flip out with a recycled prank was enormously gratifying. For the viewing audience, watching her discover the rat after she accidentally flung it to the floor, and then seeing her jump onto her bed and into the rat poo left behind, was also visually amusing.
Having received a double dose of hilarity, Ryan thought he might as well keep going as long as the girls were dumb enough to think the single pet rat was a major infestation of wild rodents. Ryan brought the rat from the hiding place in the gym back up to the living quarters. Unfortunately, the rat then got loose and it took him forty minutes to recapture it. He had thought about letting it run loose but he was afraid the girls might find a way to kill it. He decided it would be better to retire the boys' furry friend while it was undefeated and bask in the happiness of having a plan work even better than expected.