His chin
I remember Rob from most of those goofy romcoms and some mediocre action/thriller films, save "Bad Influence", in the 80s and 90s and always remembered how exaggerated his chin looked. But after all of these years I've never seen his name mentioned in those various plastic surgery rumor mills that get pinned on countless actors and mostly actresses.
Is his chin an enhancement done back in the 80s? Now that he's in his 50s and the natural progression of time and skin aging are taking root, that chin of his looks more awkward than before.