To think highly of oneself, and expect to be treated and spoiled like a little kid, resembling the Twins catcher Joe Mauer's attitude. In addition to the pompous attitude, one must not have any special talents or skills except for flaunting a big ego.
Originating from the popular MLB commercial on Youtube where Joe Mauer gives proof of his bikini-clad trip to Cabo with the host, with a photo in a frame, after the host denies ever going.