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I'm thinking of breaking down and putting P in a "big boy bed". My aunt has a twin bed that I'm planning on putting a rail on the side of. Here's the bedding I've been thinking of since it already matches his room colors and decorations:
http://www.amazon.com/All-Star-Sports-Toddler-Bedding/dp/B001GWU6IM/ref=sr_1_18?s=home-garden&ie=UTF8&qid=1313599613&sr=1-18