How I Met Your Mother Episode 4.17 The Front Porch

When Ted's girlfriend Karen finds one of Robin's earrings in his bed, she accuses him of cheating on her and breaks up with him. Ted soon learns that Lily, who couldn't stand Karen, planted the earring in his bed in order to break up the relationship. Ted goes on to discover that Lily had actually broken up several of his relationships, and had even been behind his break up with Robin. Meanwhile, the gang all gathers at Lily and Marshall's to watch Robin's new early morning news show, and Barney discovers how comfortable sleeping in a nightshirt can be.