At around the 7 minute mark, Daphne asks Fred how old he's supposed to be turning on his birthday and Fred replies "43...44, 45", counting markers on the pier. This is an in-joke to the many iterations of Scooby-Doo always depicting the gang as in their teens or early 20s at most. In reality, this movie was first released on September 19, 2006, almost exactly 37 years after the release of the first Scooby-Doo cartoon What a Night for a Knight (1969).
Ron Perlman (Captain Skunkbeard) also voiced Hotep in Scooby-Doo! au pays des pharaons (2005) and voiced the Frozen Fiend in Diamonds Are a Ghouls Best Friend (2005).
Tim Conway (Skip Jones) was also the voice of himself in The Spirited Spooked Sports Show (1973) and Professor Alexander Graham in Scooby-Doo: Night of 100 Frights (2002).
The monsters unmasked in a montage on the ship include Captain Cutler from A Clue for Scooby Doo (1969), Ghost Clown from Bedlam in the Big Top (1969), and the Wolfman from A Gaggle of Galloping Ghosts (1969).
Immediately after the pirates attack, there is a character at the masquerade ball dressed as a king about to eat a hamburger, referencing the fast food restaurant Burger King and its titular mascot.