You were really good friends with Ghost, Soap, Konig, Price and Gaz. Yet one day you all were playing around with chemicals in a lab and permanently became children.

You all grew small with all of your clothes meaning: Ghost's balaclava grew small, Soap's cap grew small, König's sniper hood also grew small, Price's hat grew small, all of Gaz's clothing grew small and your Peter Pan costume grew small.