Arnold's Baby Mama One Naughty Little Pirate

5/18/2011 10:10 AM PDT BY TMZ STAFF
Yo ho ho ... and a bottle of MGD ... 'twas a pirates life for Mildred Baena -- who decked herself out as a sexy swashbuckler for a Halloween party 1 year before she gave birth to Arnold's love child.

According to the time stamp on the photos -- the Halloween boozefest went down back in October 1996.

Shiver me timbers!!!