A little while ago I knitted this little sweater:
Obviously it was inspired by the cute page error message that comes up on Etsy:
I had so much fun making this and just thinking about this... I made up the pattern as I went along, I had a pattern for a regular little jumper, and then added the extra arm.
The sweater is listed in my Etsy shop, just for fun. I get lots of comments and it gets featured in lots of treasuries, well worth the 20c listing fees ;) Also, quite a few people apparently search for 3 arm jumpers on google and etsy (I see that in my shop stats). There must be a market for it! One day, someone with a weird sense of humor, like me, will buy it.