Watching bike racing requires some skill, or else it just looks like a bunch of guys riding together for 5 hours. However, ally cat races are usually a bit different. They are quick, fast paced, individual-centric, and usually full of people messing up.
Here is a video of a typical alley cat race start. For the most part, alley cat races have a few similar rules. All riders must race on fixed gear bikes, sometimes brakes are not allowed. The racers must race to previously determined checkpoints, the first to all checkpoints and over the finish line first is the winner. There is no determined route, you must find the quickest route on the fly.
The start to this alley cat, like many others, racers must run to their bikes which are lined up. If you've never ran in cleats before, it's not easy. It's slipper and hard to find your balance, so it makes for an entertaining start to a race with everyone slipping on the ground and over each other.