Thomas the train Pajamas set top and bottoms Toddler boys size 2T

Used Thomas the train pajamas set with top and bottom in size 2T. There is a stain on the one arm from my son going to preschool wearing these. Not sure what it is from and didn’t want to use harsh things to get it out. I believe it’s a type of marker/paint. No holes or tears, but does have some mild pilling from wear. Is a soft warm fleece that was well loved by my little one.