The Legend of Boggy Creek (1972) 
A drive-in staple of the '70s, The Legend of Boggy Creek is a dramatized documentary style film concerning the big foot phenomenon.
Sadly, it's enough to make you fall asleep in your popcorn, although I suppose in some ways it's the perfect drive-in date movie as an otherwise dull 90 minutes can instead be filled with certain other more fulfilling activities...