You could bike around on just an average bike... or you could be different and do something like below. Here are a few bikes that people got creative with. They welded roll bars on so they could do a somersault on their bike, and then keep riding.
Here's a pocketbike that has a roll bar attached to it....
Here's a bike that has two roll bars on it to make rolling easier...
Last, but not least, here's a bike that rolls over... a lot...
