I actually do that all the time! I'm almost 22 and i keep saying that i'm 20. Guess its just wishful thinking. Doesn't help that every time i go to the movies someone cards me, because they think i'm no older then 16.
When i was up at Will's brothers for the weekend we went to a bar for food, because his brother and friend were getting a beer sampler, we were all carded, he looked at me and Will's cards and was like "Well either you guys look really damn young for your age, or these are be best damn fake ID's I've ever seen." Had to ask his co-worker to look at our ID's because they couldn't believe we were 21. Funny part is we weren't even drinking!!!