When ABC's Castle returns on Monday, Rick Castle's apartment is going to be bursting at the seams.Winter TV Preview: Get scoop on all the must-watch new showsAs we first reported, the episode, titled "Significant Others," finds Castle (Nathan Fillion) in a pickle when his "deep-fried Twinkie" ex-wife Meredith (Scandal's Darby Stanchfield) winds up crashing at Casa Castle after her planned trip to Europe falls through because Alexis (Molly Quinn) has mono. As luck would have it, Beckett (Stana Katic) is also sleeping over while her place is being fumigated.Can we say awkward? In any case, based on our exclusive first look at the episode below, Beckett is a little bit unsure about to handle the threat of Meredith. Fortunately, Lanie (Tamala Jones) is there to see Beckett straight.Exclusive: Look who's coming back to Castle!"This is a war, girl, and guess who's losing?" Lanie warns. So, will Lanie get Beckett ready to fight the battle ahead? Watch the exclusive preview below.Castle airs on Mondays at 10/9c on ABC.