The Hemogoblin, Haniver and Tzitzmitl from Be Cool, Scooby-Doo's "Mysteries on the Disorient Express" all appear on movie posters seven episodes later in "Silver Scream." "Monaco," an Archie Barnes film also appears on a movie poster, which is a reference to Jake Monaco who was the composer for the music in Be Cool, Scooby-Doo!.
As a bonus fun tidbit from "Mysteries in the Disorient Express," the gang lists all 8 monsters from the episode towards the end, but misses Tarasque.
Thanks to Samuel Kirkwood for sharing this fun fact!
~ WildwindVampire ~