Shout Out / The Return to Gravity Falls

• Starter Villain Montana Jeffreys and his two talking dogs parody both Indiana Jones and Up.
• The company that is helping to build the Manor is Weytani-Yuland.
• In addition to being a spoof of Dungeons & Dragons, the Strongholds and Serpents game the gang plays in the episode is cursed, taking elements from Jumanji.
• To beat the ghost/poltergeist/tulpa thing, the Manor residents and the N.P.P.P. sang a Bohemian Parody.
• The episode A Summerween Carol is a parody of A Christmas Carol, with Stan as Scrooge and the ghosts being Mabel, Soos, and Ford.
• The twins' Summerween costumes are Obi-Wan Kenobi and Anakin Skywalker.
• Magenta, the Dragon Pacifica gets, is a Monstrous Nightmare.
• The Djinn in I Dream of Deals is named William Cardinal.
• The first real episode of Season Three is called Daybreak and focuses on Mabel helping a boy vampire and a girl werewolf fall in love. The first cryptogram even gives alternate titles which include "Still better than Twilight."
• The Paths combines martial arts and elemental control, although we've only really see fire in action before. A movie called Evotar: The Last Spacebender is also mentioned.
• In the episode before, EZB gives the title of the next episode, The Haunted Mansion, saying that it is exactly what it sounds like, complete with Constance, Edward, and hitchhiking ghosts, although the latter don't show up until the next episode.
• One of EZB's deaths is being zapped by a Dalek and McGucket and Ford's code-names when they create Summerween are Doctor Timey and Mister Wimey.
• The episode Soos-Less takes it's main plot point from It's a Wonderful Life, although instead of Soos' complete absence from history, the event that is changed is that he never worked at the Mystery Shack.
• A girl who is who is eventually revealed to be Coraline shows up in Ye-Olde Fair Wells, and it's heavily implied that she will return. Then Word of God hints at Norman being a semi-recurring character in the Montana Jeffreys episode, although his potential return is questionable. Odds are good that, if the story ever gets finished, the entire Mystery Kids gang will get together at some point.
• In the first part of The Rising Grasp, one of the Guardsman's students mention hearing that Paris got their first pair of superheroes who are currently fighting a rock golem, and EZB's death for that chapter is becoming collateral damage of said heroes' fight with the creature.