Best Answer - Chosen by Asker
The letter limit for your username is 12, and only could have numbers, letters and spaces. The least amount of characters your username can be is four, but back in the beginning of Club Penguin, your name could have been 2 letters or just numbers. If your penguin name is inappropriate or not yet confirmed, your name will be "P" and then a small code of numbers, the numbers are what number of penguin you are.
Or it is a possible glitch.