the car on the cover of the first Midnight Club is Dustin's mx-6, his car was even in some pep-boy's ads.Thers a yellow kitted mx-6 on the cover of one of the midnight club video games. If not those then one of the street racing games.
there is a 1st gen mx6 in "Happy Gilmore" when adam sandler is walking into the country club the first time he plays golf. it's in the parking lot somewhere.
have also seen a 1st gen mx6 on an episode of "seinfeld", just couldn't tell you which episode.
and a 2nd gen probe gets ran over by the monster truck of a batmobile near the end of "batman begins"