Hexaflexagons are hexagonal folded bits of paper that can be inverted onto themselves to show multiple faces. Watch the video for more information, the reason this phenomenon happens is that the Hexaflexagons are a flattened out folded up Möbius strip. I had a go at this yesterday using patterns I found on the flexagon portal it’s quite simple.
I think these would make for some pretty cool business cards.
Vihart actually posts quite a lot of cool maths related videos, it’s worth checking them out.