Can I use fleece in a pattern if it’s not listed in the fabrics to use?

I bought a ‘Sew Easy’ pattern from Wal-Mart yesterday for a pair of mens or womans pajama pants. It says to use cotton or cotton blends. Would it be OK if I used fleece instead? I don’t see why it would cause a problem but I am still a beginner so I thought I would ask for advice.

Also, are there any special instructions for working with fleece? I’d like to whip up some PJ’s as Christmas presents.