When I was a kid, one of the coolest things I saw on TV and desperately wished I could do myself was when someone reached into their jacket and pulled something (gun, handkerchief, pocket watch) from the cool inside pocket.
Turns out this is perfectly achievable without sewing anything, purchasing a suit or jacket, or being suitably attired for a ballroom dancing competition.
Simply put on a dressing gown (or robe, if you’re one of those people) inside out. Shazam! A cool inside pocket - maybe even more than one - with all the comfort of loungewear.