Photo & Video via YouTube Hendrik Ball
Tim bought these Japanese Zip Bags back in 1984, and as well as being fun, they are an interesting example of topology! Essentially a long strip of tough fabric with an attached zip, when you do the zip up, it becomes a useful bag. Depending on the distance from the start of the zip to the end of the strip, 4 different shapes of bag are possible. In addition, you can even combine 2 strips, to make a bigger bag.