These videos were made by Vi Hart. Check out other videos of this youtuber. If you like these videos, please subscribe to her channel.
These videos below are amazing paper folding magic. Her narration is also very good. I really enjoyed watching these.
Here is part 1
Here's part 2
Attention: Hexaflexagon Safety Guide
Historical Note: This video is based on a true story. Arthur H. Stone really did invent the hexaflexagon after playing with the paper strips he'd cut off his too-wide British paper, and really did start a flexagon committee. The details and dialogue, however, are my own invention.
This video is based on, and in honor of, Martin Gardner's first Mathematical Games column from 1956, "Hexaflexagons," which can be found here: http://maa.org/pubs/focus/Gardner_Hexaflexagons12_1956.pdf