Barney finally meets his dad, Jerry (guest star John Lithgow)

Barney realizes he has heartfelt affection for Nora, and he thinks that something is wrong with him; and Robin dates a guy who acts like a dog.

Marshall becomes obsessed with saving the environment after seeing a documentary on garbage; Ted runs into The Captain; Barney admits he has feelings for a woman.

Barney declares Feb. 13 a holiday for desperate women; Marshall receives a Valentine's Day surprise from Lily; Zoey and Ted work on figuring out their relationship.

Zoey arranges a date for Ted with her cousin, played by Katy Perry; and Ted realizes he has feelings for Zoey, and tells his friends he needs an intervention

Marshall and Lily try to figure out how to conceive a baby with the gender of their choice; Robin's perky new co-anchor irritates her.

Ted becomes conflicted after meeting an attractive woman who is passionate about saving the landmark building being torn down for his new project.

When the gang teases Robin about not being a real New Yorker, she sets out to prove them wrong by racing to catch a glimpse of Woody Allen.

Barney uses his best womanizing tactics to try to convince Ted to design the new GNB building; Robin drunk dials Don.

When the gang helps Barney's mother move, they learn that she has lied to him about events throughout his life; Robin oversells Ted to a blind date.

Ted runs into an ex-girlfriend (Rachel Bilson); Robin is upset over Don; Marshall can't stop talking about his desire to start a family.