'Wet Hot American Summer' Star -- Reunion Series is HILARIOUS ... Fans Will Be Happy

Relax "Wet Hot American Summer" fans ... one of the main stars promises they won't pull a "Dumb and Dumber To" with the TV reboot of the summer camp classic.

Marguerite Moreau -- who played Katie in the original W.H.A.S. movie in 2001 -- was outside Urth Cafe Friday when she gushed about reuniting with her co-stars. Netflix is shooting an 8 episode series with most of the original cast ... including Amy Poehler, Bradley Cooper and Paul Rudd.

It's a cool reunion ... since most of the A-listers weren't huge stars back in 2001.