Rue McClanahan Secret Dirty Jokes

6/5/2010 4:30 AM PDT
Rue McClanahan will truly be missed ... for her smile, her compassion ... and her ability to tell a dirty joke.

TMZ obtained footage of Rue and her gal pal Betty White from 1985 -- in which the ladies swap some R-rated humor ... and it's pretty damn hilarious.

RIP Rue.