Halloween on a budget: Is it okay to use pajamas as a Halloween costume?

Last year my son was 19 months and I put (he already had) jeans, flanel shirt, blue jean jacket and bought a $5 cowboy hat, hehe. I was going to say depends but those pjs are perfect for a costume. They look just like a costume of a skeleton youd buy so Id deffinetly go with that, your son will be what? 11 months, he will never wear this yrs costume again anyway.