Specifically very large, shiny, red heels. Fair play to James Corden's production team for managing to track down a pair of red patent stilettos in Pratt's large specifications (do enjoy Howard's guffaw when he makes reference to his large hoofs). What does sadden us slightly is that we don't get to see Pratt wrestle them on to his feet. It must've taken quite a long time. We would've watched. 

As for how Pratt deals with running around in heels, well, he's pure poetry in motion. Eat your heart out 'Claire'.