Curse of the Lake Monster is the sequel to Scooby-Doo!
The Mystery Begins which was produced by Warner Premiere.
Velma warns them that often when two people in a group start dating, any changes of that relationship affects the whole group, but the two don't seem to care. They stop at a small country store called Trowburg's Gas & Goods where a seemingly crazy woman tells them that she warned them not to build the country club, and that the lake monster will return.
The lake monster falls, however, falls and turns out to be Mr.
He shows them to their quarters, and when Shaggy is getting his bags off the top of the Mystery Machine, he falls off and is caught by Velma, who he then falls in love with.
Shaggy asks Scooby if there is any chance of him and Velma, and Scooby bursts into laughter.
He and Scooby then fantasize the entire school celebrating a Hawaiian-themed party, until Velma cuts it off.
Velma and Shaggy wait by the van for Fred and Daphne so they can go to meet Daphne's uncle, who has given them summer jobs at his country club in Erie Pointe so the gang can pay for the damages they did to Old Man Frickert's barn (setting it on fire) during one of their mysteries.
They paid no attention to her, so she used her magic staff - which used moonstones as the source of her power - to turn a frog into a horrible monster that attacked the villagers. He eats the napkin when she appears, and tells her that Fred is off putting with some girls.