Mighty Mouse Syndrome
Someone who thinks they are like the cartoon character, Mighty Mouse..."here I am to save the day!" A coward who suddenly finds the 'courage' to tell everyone how he would have been the hero in a situation.
i.e. Mark Wahlberg claimed that he would've been able to single-handedly over-power the 9/11 terrorists and prevent a plane from crashing. Mark has 'Mighty Mouse Syndrome'.