Ash's Adventures of Big Fat Liar is another upcoming Pokemon crossover film planned to be made by Shadow101815. It will appear on Google Drive in the near future.
Ash Ketchum, Scooby-Doo, Remy the Rat, Hiccup, Tino Tonitini, Mario, and their friends meet Jason Shepherd (whom Ash, Scooby, Shaggy, and Tino are bonding and hanging out with), a 14-year-old chronic liar living in the town of Greenbury, Michigan who is constantly deceiving and misleading his way out of trouble. He tries to get out of writing his 1000 word essay by making up a lie, but he gets caught by his English teacher, Ms. Phyllis Caldwell, who alerts his parents, Harry and Carol Shepherd. He is given three hours to submit his essay, otherwise he will fail English and go to summer school. In a rush to turn it in, he accidentally forgets it in the limousine of Hollywood producer Marty Wolf, whom The Crime Empire and Percival C. McLeach work for and who gives him a ride to the community college to turn it in after he is hit by the limousine. Marty initially attempts to give it back to him, but when he sees that it is excellent, it inspires him, and he decides to keep it for himself.
Jason realizes his essay is missing and tries to explain what happened when he met Marty, but neither his parents or Ms. Caldwell believe him, and he is sent to summer school. Later, after a disgusting first day there, he and his best friend, Kaylee, go to see a film, and upon watching the previews, they realize that Marty has plagiarized his essay and is turning it into a film. They fly to Los Angeles to confront him, as Jason is determined to convince his parents that he truly wrote his essay. Upon their arrival, they trick the limo driver and struggling actor Frank Jackson into giving them a ride to Marty's studio, where Jason creates a distraction, with help from Kaylee, that tricks its receptionist, Astrid Barker, into letting him speak with Marty in his office. Jason sneaks into there to convince him to call his father and tell him that he stole the essay, but instead he "accidentally" burns it and removes him and Kaylee from his office. Angered, they plan to inconvenience him until he admits to having stolen it. Frank, having discovered their true identities, joins them in their plan, as he has had a troubled history with Marty. After gathering information about his cruel and abusive treatment of his employees, they sabotage him by going as far as pouring blue dye in his pool and orange food coloring in his shampoo, putting super glue on his headset, sending him to a child's birthday party where he is mistaken for the hired clown and beaten up by the young guests, and modifying the controls to his car. Their tampering with his car causes numerous controls to perform the incorrect function, such as the brake pedal sounding the horn and the radio playing "Blue (Da Ba Dee)" as a way of mocking his blue skin. Struggling to control his car, he stops just behind a monster truck, but is later rear ended by an old lady, whom he had insulted earlier. He accidentally crashes into the monster truck, causing its driver, a wrestler known as "The Masher", to destroy his car in anger.
These pranks cause Marty to miss his appointment with his boss and the president of Universal Pictures, Marcus Duncan. After another film produced by Marty, Whitaker and Fowl, proves to be a critical and commercial failure, Duncan loses confidence in him and threatens to pull production for Big Fat Liar. Jason approaches Marty and agrees to help him in exchange for his confession to having stolen the story. Guided by Jason, he makes a successful presentation which convinces Duncan's wife, Shandra (Chris Ott), to green-light Big Fat Liar, but Duncan warns Marty that any mistakes will cause Universal to pull funding for it and end his career. Marty, however, betrays Jason again and kicks him and Kaylee out from their hiding place in a warehouse of Universal Studios. His assistant, Monty Kirkham, having grown tired of being bossed around and abused by him, decides to help Jason and Kaylee to expose him. They rally all of his employees and devise a plan to stop him once and for all.
The next morning, as Marty heads to the studio to begin shooting, many of his employees cause him to be late through multiple mishaps. As Marty finally arrives at the studio, he witnesses Jason kidnapping his stuffed monkey, Mr. Funny Bones. After a chase across the studio, he childishly and prematurely celebrates his supposed victory, mocking Jason and telling him that he will never tell the truth, as well as admitting that he stole Jason's story, thinking that he will still get away with it. However, the altercation is then revealed to be caught on twelve different cameras and is witnessed by many people including his employees, the news media, Jason's parents, and Duncan. Disgusted that Marty would steal a story from a young boy, Duncan immediately fires him due to his acts of plagiarism and dishonesty. Jason thanks Marty for teaching him the importance of telling the truth. After escaping from him and reuniting with his parents, Jason finally re-establishes his trust with them.
Universal later reproduces Big Fat Liar, utilizing the talents and skills of all those whom Marty had abused, and it is released in theaters, with Jason being credited during the closing credits for having written the original story. Meanwhile, Marty, having been stripped of his career, declares bankruptcy and begins his new job as a birthday clown. Unfortunately, he is recognized by The Masher, who orders his son, Darren, the birthday boy, to show Marty his "butt-kicker" manoeuvre. Marty screams in horror as Darren charges at him and kicks his crotch, causing him to groan in pain.
- Delia Ketchum, Professor Oak, Scooby-Doo, Shaggy Rogers, Fred Jones, Daphne Blake, Velma Dinkley, Scrappy-Doo, Remy the Rat, Emile, Hiccup, Toothless, Astrid, Stormfly, Fishlegs, Meatlug, Snotlout, Hookfang, Ruffnut and Tuffnut, Barf and Belch, Gobber the Belch, Heather (How to Train Your Dragon), Windshear, Gustav Larson, Fanghook, Eret, Skullcrusher, Tino Tonitini, Lor McQuarrie, Carver René Descartes, Tish Katsufrakis, The Crime Empire (excluding Poison Ivy), Percival C. McLeach, Captain Gutt, Flynn, Squint, Raz, Silas, Gupta, Dobson, and Drago Bludvist will guest star in this film.
- Like the Big Fat Liar segment featured in Pooh's Adventures of Scooby-Doo and the Ghoul School (in which most of that film's guest villains will work for Marty Wolf), The Crime Empire (excluding Poison Ivy), Percival C. McLeach, Captain Crew, Flynn, Squint, Raz, Silas, Gupta, Dobson, and Drago Bludvist will work for Marty Wolf in this film.
- Like in Pooh's Adventures of Scooby-Doo and the Ghoul School (which features Big Fat Liar as a segment), the only changes to this film are that the H word, the words "crap", "Oh, my God!", "Rick R*****o", "geek boy", "Eat my boobies", "sp**", and "You suck!" will be replaced with the words "heck", "crud", "Oh, my gosh!" (for most parts), "Rick Idiot-ton", "nerd boy", "Touch my chest", "jerk", and "You stink!", The Masher will say to his son Darren "Show me the butt-kicker!" instead of "Show me the nutcracker!" (as that line refers to kicking Marty Wolf in his private area), Frank Jackson's fourth-wall-break line "I've got some R-rated dialogue for you, but I'm gonna keep it PG. I'm gonna keep it PG." will be shortened to "I've got some R-rated dialogue for you, but I'm gonna keep it G. I'm gonna keep it G." (due to the real film's PG rating), Marty Wolf's screaming line will be shortened from "Oh, my God!" to "Oh, my...aah!" when he discovers that his skin and hair have been dyed to blue and orange, and the brief bits forming buttocks, the brief alcohol drinking bits, and the brief smoking scene will be removed to make the film more G-rated, due to the Pokemon franchise being made for children.
- The main reason why Scooby-Doo and the gang's real counterparts and Scrappy-Doo are guest starring in this film is because they will be absent in the Big Fat Liar segment featured in Pooh's Adventures of Scooby-Doo and the Ghoul School.
- Both Pokemon 4Ever, Scooby-Doo, and Big Fat Liar were released in theaters in 2002, the same year What's New, Scooby-Doo? was first broadcast on television.
- Big Fat Liar was first released on Blu-ray in 2014, the same year How to Train Your Dragon 2 was released in theaters and Scooby-Doo! Frankencreepy was released directly to DVD.
- The storyline continues in Ash's Adventures of Bigger Fatter Liar.