Used by morons who are either too stupid, young, or lazy to make themselves aware of the original meaning of the phrase "In like FLYNN." Originated from the actor ERROL FLYNN, who was an early twentieth century actor well known for being a ladies man.
Next time you hear someone say 'in like flint' slap them unless they're talking about the 1967 movie by the same title.
I really liked James Coburn's acting in "in like FLINT." If I was that smooth, I'd be "in like FLYNN" with the ladies.