On the website of sculptor and mathematician George Hart, there are step-by-step instructions for how to craft a Möbius strip from a single bagel. I like his thoughts at the very end of the instruction process:

"It is much more fun to put cream cheese on these bagels than on an ordinary bagel. In additional to the intellectual stimulation, you get more cream cheese, because there is slightly more surface area."

Mathematically Correct Breakfast: How to Slice a Bagel into Two Linked Halves (via Serious Eats NY, thanks Laura)