I signed my passport when I was 10 years old, when I applied for it the first time. I am but 20 now. It is almost time to renew it. The signature that I gave for the first time is very... childish (and cute :)). Is it possible to change it during the renewal? Say, if I couldn't, will I be able to use a new one in the country that I travel to (filling out official documents and such)? Will they check every signature that I put with the one in my passport?
Signing a passport is a requirement for each new passport. As much as anything else your signature acknowledges that you have read its terms and conditions, and that you took possession of it.
There is no requirement that signatures remain consistent throughout a person's life time. In your specific case, there would be thousands of applicants in a similar situation. Not just children, but older folks also whose signature changes. The examiner who processes your application will have seen the same situation countless times.