Underage 'Teen Mom' Coronas and Beer Bongs

1/27/2011 11:00 AM PST BY TMZ STAFF
19-year-old "Teen Mom" Maci must have misplaced her Shirley Temple -- because TMZ has obtained some pretty crazy pics of the MTV reality star brewing up serious trouble ... and hitting a beer bong.

No word on when exactly the alcohol-infused party pics were taken -- but thankfully, Maci doesn't look pregnant at the time. 

MTV had no comment.