This article is from the Problem Behaviors in Cats FAQ, posted to rec.pets.cats newsgroup. Maintained by Cindy Tittle Moore with numerous contributions by others.
Cats are notorious for waking their owners up at oh-dark-thirty. If you wish to stop this, there are several steps to take.
The cat may simply be hungry and demanding its food. By feeding it when it wakes you up at an ungodly hour, you are simply reinforcing its behavior. If this is why it's waking you up, you can handle this either by filling the bowl just before you go to sleep so it will not be empty in the morning, or by ignoring the cat's wakeups and feeding it at the exact same time convenient to you every morning. The cat will adjust fairly quickly to the second.
If it is trying to play, there are again several tactics you can try. If you make a practice of tiring it out with play just before bedtime, you can reduce its calls for play at dawn. What works in some cases is to hiss gently at the cat. You can also try shutting it out of the bedroom. If it pounds on the door, put it in a bathroom until you wake up.
In persistent cases, try the vacuum cleaner, eater of noisy kitties. Go to bed, leaving him out in the hall. Position the vacuum cleaner next to the door, inside it. Plug the vacuum in, and arrange things so you can switch the vacuum on from your bed (eg, wire a switch into an extension cord). Wait for the scratching and wailing at the door. Turn the vacuum cleaner on. If cat comes back, turn it on again. The cat will eventually decide to stop bothering you in the morning.