Marshall bequeaths a "slap bet" slap to Ted and Robin; Lily's estranged father (Chris Elliott) visits for... Full summary

After breaking up with Robin, Barney pulls out all of his greatest tricks to get back into the dating scene.

When Robin and Barney hit a rough patch in their relationship, Lily tries to break them up.

Barney's know-it-all attitude gets him in hot water with Robin; Marshall and Lily offer relationship advice.

Barney wants Robin to become an American citizen; Lily joins Marshall and Ted on their road trip.

Lily and Marshall come on too strong to impress Robin and Barney, who then try to break off the double-dating.

Robin investigates when she thinks Barney is cheating on her, only to find that he is spending his time with Ted,... Full summary

Ted realizes that the girl he goes on a blind date with is actually someone he dated years earlier, and that they... Full summary

Lily forces Barney and Robin to face their fears about defining their relationship; Ted is anxious about his first... Full summary

In the fourth-season finale, Ted works feverishly to promote his business while Marshall tries to get him to the roof... Full summary