John Leguizamo Says Patrick Swayze 'Couldn't Keep Up' on 'To Wong Foo'

John Leguizamo is kinda speaking ill of the dead -- labeling the late Patrick Swayze as insecure while shooting a movie in the '90s ... with some other descriptions to boot.

The actor was talking to Andy Cohen on his SiriusXM radio show this week -- and they started discussing JL's '95 comedy 'To Wong Foo' ... in which Pat, John and Wesley Snipes portrayed drag queens and shared the spotlight together on camera.

Andy tells John he'd only heard wonderful things about Patrick -- but when John hesitates to confirm that ... they get into a little gossip, with John describing them butting heads on set.

Take a listen for yourself ... long story short, JL claims Patrick was "insecure" and "neurotic" while they were filming -- and, apparently, much of it had to do with the improv John and Wesley were doing with their characters, often going off script and making up lines.

John says Patrick got irked by that, and would ask them to stick to the script -- something John says he wasn't willing to do ... as he wanted to bring some flare and flash to his character, which he says was lacking in the OG draft.

He also claims Patrick simply couldn't keep up ... and it seems to have caused problems.