He's been neutered from a young age and always enjoyed a good peddle on said dressing gown. Recently he's started peddling more passionately with all four feet and chewing/sucking the dressing gown and turning round in circles so it gets all twisted up.
Just a phase? I think it's strange he's suddenly started doing it. I've owned cats most of my life and never known one do this before.
I hasten to add, I'm not actually wearing the dressing gown while this is happening!