Why are these called "pandas?" Well, ya see, there's this rad chick who goes by the name faster panda kill kill. She takes rad self-portraits while riding her bike. They are so rad, in fact, that a group was formed to record similar self-portraits cuz, really, just about anyone who has a camera and rides bikes also takes these self-portraits.
Example:
(No, that's not upside-down; it's a panda. Dig it.)
We trust your judgment -- if you've joined the pool, you've either been invited by another member and are assumed to get it (the concept of a panda, that is), or you've found us and joined because you think the photos you've seen are fun, do it yourself, and therefore also get it. And really, if you ride a bike and have a camera and DON'T take any photos of this type, then you're probably violating the first rule of pandas anyway.