UNICEF Goodwill Ambassador Katy Perry delivers a special weather report on the devastating effects of climate change for the world’s children.

For the body and the mind: Try out some knee exercises and learn some new vocabulary related to posture and fitness. Enjoy!

From time to time, we give celebrities a chance to read some of the mean things people tweet about them. We extended that same offer to our Commander in Chief, who happily agreed. This is an all President Obama edition of #MeanTweets.

This video shows us that Shakespeare invented over 2000 new words and phrases, such as "eyeball," "anchovy," and "puppy."

Red simply doesn't want to wake up for school! David struggles to get him out the door, but there is something important that he is forgetting...

Barney never fails to impress the group with the lengths he'll go in order to get a woman interested in him.

Red meets David's friends Debs and Darrell, and their children Charlie and Holly. While playing hide and seek with Charlie and Holly, Red finds the perfect hiding place.

In this week's Lightning Round, Neil Patrick Harris and Billy Eichner take to the streets to find out how New Yorkers feel about the end of the series How I Met Your Mother.

Jimmy Fallon can't believe he's at the White House on the Fourth of July. Watch part of his stand-up performance from that evening in which he does impressions of ten other comedians!

Minidisco presents a song that reviews the names of the family members as well as the names of the different fingers! Enjoy!

Have you ever wondered why English seems to have roots in so many different languages? Here is a look at what words the Anglo-Saxons and Vikings brought to the English language.

Penny invents a quiz to find out whether Sheldon or Leonard is smarter, which only reveals that both of them are completely uninformed about popular culture with the exception of Star Trek.

The cover letter is an essential document when submitting a job application. Here you can learn about what function a cover letter should serve.

When Penny returns from visiting her family in Nebraska, Leonard is happy to see her. Sheldon, however, is much less welcoming when he learns that her family has the flu.

Leonard finally tells Penny how Sheldon saved his life and broke the elevator at the same time.