The Klein Bottle is an item that is only available in Stick RPG 2. It is also one of the three 4th dimension objects that the player must collect and give to Professor Ansel, in order to unlock The Lab and beat the game.
A way to find the Klein Bottle is to go to The Club on the third island and find a stick figure named Broski. He should be the second person standing from the bartender counting from the left. If you have sufficent strength (390+) he will challenge you to an arm wrestling contest and by winning he'll give you a Klein Bottle.
Another way to find the Klein Bottle is to go to the third island and take a left, you will see The Squeegee Kid by the dumpster, he will be there in the evening. He will ask to find his squeegee. Once you have known what you need to do go to Wally Mart, and buy the Painkillers or the Self Help Book. Then you will need go to the first island and go to the bottom right corner. There will be a man on the edge. Give him the painkillers or the book and he will give you a squeegee. If you give him the painkillers he will jump off, but if you have sufficient Charm and the Self Help Book, you can dissuade him from suicide. Then go back to The Squeegee Kid. Give him the squeegee and he will give you a Klein Bottle.
Like the other 4th Dimensional Objects, a Klein Bottle can also be purchased from A Dimensional Drifter at an exorbitant price.
A Klein bottle is a non-orientable surface. Dissecting it along its plane of symmetry yields two Möbius strips.