Ryan, Winnie the Pooh, Ash, Michelle and the rest of their friends meet David Gordon (John Cusack), a popular science fiction author, was widowed when his wife Mary died as they were trying to adopt a child. Two years later, David is finally matched with a young boy named Dennis (Bobby Coleman). Socially awkward, Dennis believes he is from Mars and only goes outdoors when under the cover of a large box to block out the sun's harmful rays. Although initially hesitant to adopt a boy by himself, David recognizes a part of him in Dennis and slowly coaxes him out of the box and into his home.
With the help of David's friend Harlee (Amanda Peet) and sister Liz (played by Cusack's real life sister Joan), David and Dennis begin an arduous process of learning about each other, from Dennis's incessant photo-taking habits, his inclination to eat only Lucky Charms, and his perpetual stealing, to David's continuing love of his wife, his love of baseball and his own struggles to be accepted by others.
As Ryan, Winnie the Pooh, Ash, Michelle, the rest of their friends and David teaches Dennis how to be an "Earthling," father and son earn each other's trust and eventually find someone who will love them unequivocally.
- Bobby, Cindy, Oliver, Matthew, Dwayne, Steve, DJ, Stephanie, Michelle, Malcolm, Resse, Dewey, Mallory, Renee, Daisy, Gabriella, Gerald, May, Sid, Kady, Franklin and The Gang, Alvin, Simon, Theodore, Brittany, Jeanette, Elanor, Ben Hilton, Jamie, Max, Becca, Nicky, Jeannie, The Flash/Tony, Crispin, Dylan, Duncan, Sean, Tony's Brother, German Speaking Boy, Juel, Erin, Benny, Lina, Henry, Kiki, Dennis The Menace & Friends, Pete & Pete, Richelle, Littlefoot, Cera, Ducky, Petrie, Spike, SpongeBob SquarePants, Patrick Star, Bloom, Stella, Flora, Musa, Tecna, Layla, Roxy, Simba, Timon, Pumbaa, Zazu, Terk, Tantor, Baloo, Bagheera, King Louie, the Vultures (Buzzie, Flaps, Ziggy, and Dizzy), Jiminy Cricket, Alex, Marty, Melman, Gloria, the Penguins of Madagascar (Skipper, Kolwalski, Rico, and Private), Genie, Louis, Roger Rabbit, Danny, Sawyer, Rex, Dweeb, Woog, Esla, Rapunzel, Pascal, Flynn Rider, Maximus, Jean-Bob, Speed, Puffin, Chanticleer, Wilbur the Albatross, Owen, Lindsay, Beth, Strawberry Shortcake and her friends, Danny Phantom, Sam Manson, Tucker Foley, Jazz Fenton, Danny, Sawyer, Jean-Bob, Speed, Buddy, Tiny, Puffin, Rex, Dweeb, Woog, Elsa, Rapunzel, Pascal, Flynn Rider, Maximus, Chanticleer, Wilbur the Albatross, Bob the Tomato, Larry the Cucumber, Junior Asparagus, Hercules, Megara, Philoctetes, Pegasus, Alice, Pocahontas, Meeko, Flit, Princess Aurora, Prince Phillip, Peter Pan, Tinkerbell, Rosetta, Silvermist, Idressa, Fawn, Oliver, Dodger, Lucky, Cadpig, Rolly, Spot the Chicken, Woody, Buzz Lightyear, Jessie, Tommy Pickles, Chuckie Finster, Simon, Theodore, Brittany, Huckle, Lowly, Woody Woodpecker, Ord, Cassie, Arthur Read Ash and his friends, Ronald McDonald and his friends, Bob the Tomato, Larry the Cucumber, Junior Asparagus, Laura Carrot, Jimmy and Jerry Gourd, Mr. Nezzer, Mr. Lunt, the Powerpuff Girls (Blossom, Bubbles, and Buttercup), Professor Utonium, Miss Keane, Blue the Puppy, Ploka Dots, Slippery Soap, Tickety Tock, Mr. Salt, Mrs. Pepper, Paprika, Periwinkle, Roar E. Saurus, Fredrica the Birthday Girl, Zazu, Rafiki, Kovu, Kiara, Terk, Tantor, the All-Grown Up Gang, Grandpa Lou Pickles, Carly Shay, Sam Puckett, Freddie Benson, Spencer Shay, Gibby, The Gummi Bears, Scrooge McDuck, Huey, Dewey, Louie, Webby, Launchpad McQuack, Darkwing Duck, Gosalyn Mallard, Honker Muddlefoot, Chip and Dale, Gadget Hackwrench, Monterey Jack, Zipper, Lilo, Stitch, Pleakey, Jumba, the Muppets (Kermit the Frog, Miss Piggy, Fozzie Bear, Gonzo, Bean Bunny, Rowlf the Dog, Scooter, Rizzo the Rat, Waldorf and Statler, Pepe the King Prawn, Sweetums, Thog, Sam the Eagle, the Electric Mayhem and Walter), Popeye, Olive Oyl, Popeye's Nephews (Peepeye, Poopeye, Pipeye, and Pupeye), Wimpy, Mario, Luigi, Princess Toadstool, Toad, Yoshi, Donkey Kong, Diddy Kong, Sonic the Hedgehog, Miles "Tails" Prower, Knuckles the Echidna, Amy Rose, Cream the Rabbit, Cheese the Chao, Shadow the Hedgehog, Rouge the Bat, Team Chaotix (Vector the Crocodile, Espio the Chameleon, and Charmy the Bee), Silver the Hedgehog, Blaze the Cat, Spyro the Dragon, Sparx the Dragonfly, Banjo and Kazooie, The Griffins (Peter, Lois, Chris, Meg, Brian, and Stewie), Glenn Quagmire, Cleveland Brown, The Teenage Mutant Ninja Turtles, Harry Potter, Hermoine Granger, Ron Weasley, Anastasia, Alex, Marty, Melman, Gloria, the Penguins of Madagascar (Skipper, Kowalski, Rico, and Private), King Julien, Maurice, Mort, Vitaly, Gia, Stefano, Marlene, Baloo, Bagheera, King Louie, Kit Cloudkicker, Rebecca Cunningham, the Vultures, Pinocchio, Jiminy Cricket, Geppetto, Woody, Buzz Lightyear, Jessie, Hamm, Slinky Dog, Rex, Mr. Potato Head, Mrs. Potato Head, the Squeeze Toy Aliens, Bullseye, Dolly, Mr. Pricklepants, Buttercup, Trixie, Chuckles the Clown, the Incredibles (Bob, Helen, Dash, Violet, Jack-Jack, and Frozone), Cinderella, Snow White, Ariel, Sebastian, Belle, Lumiere, Cogsworth, Mrs. Potts, Chip the Cup, Aladdin, Princess Jasmine, Genie, Abu, Mulan, Mushu, Cri-Kee, Pocahontas, Meeko, Flit, Princess Aurora, Princess Tiana, Louis, Rapunzel, Flynn Rider, Pascal, Maximus, Princess Merida, Peter Pan, Tinker Bell, Terence, Fawn, Rosetta, Silvermist, Iridessa, Vidia, Lucky, Cadpig, Rolly, Spot the Chicken, Alice, Hercules, Megara, Phlioctetes, Pegasus, Phineas and Ferb, Candace Flynn, Isabella Garcia-Shapiro, Stacy Hirano, Buford, Baljeet, Perry the Platypus, Kids World's Adventures Team, and the characters will guest star in this film.