[2] Featuring the voices of John Goodman, Billy Crystal, Steve Buscemi, James Coburn, Mary Gibbs, and Jennifer Tilly, the film was directed by Pete Docter, co-directed by Lee Unkrich and David Silverman, and produced by Darla K. Anderson, from a screenplay by Andrew Stanton and Daniel Gerson.

However, the monster world believes that the children are toxic, and when a little human girl, Boo (Gibbs), sneaks into the factory, she must be returned home before it is too late.

Monsters, Inc. premiered at the El Capitan Theatre in Los Angeles on October 28, 2001, and was released in theaters in the United States on November 2.

One evening after work, top scarer James P. "Sulley" Sullivan discovers that an active door has been left in the station of his rival, Randall Boggs.

Chaos erupts when other monsters see the girl; Sulley and Mike escape with her as the Child Detection Agency (CDA) arrives and quarantines the restaurant.

[13] By early February 1997, Docter, together with Harley Jessup, Jill Culton, and Jeff Pidgeon, had drafted a treatment that bore some resemblance to the final film.

[15] The film would be the first Pixar feature not directed by Lasseter, helmed instead by Docter, as well as Lee Unkrich and David Silverman, who served as co-directors.

[17] Docter's original idea featured a 30-year-old man dealing with monsters that he drew in a book as a child coming back to bother him as an adult.

[23][24] The voice role of Sulley went to John Goodman, the longtime co-star of the comedy series Roseanne and a regular in the films of the Coen brothers.

"[25] Billy Crystal, regretting having turned down the part of Buzz Lightyear years prior, accepted that of Mike Wazowski, Sulley's one-eyed best friend and scare assistant.

[25] In production, the film differed from earlier Pixar features, as every main character in this movie had its own lead animator – John Kahrs on Sulley, Andrew Gordon on Mike, and Dave DeVan on Boo.

To help the animators with Sulley and other large monsters, Pixar arranged for Rodger Kram, a University of California, Berkeley expert on the locomotion of heavy mammals, to lecture on the subject.

Other production houses had tackled realistic fur, most notably Rhythm & Hues in its 1993 polar bear commercials for Coca-Cola and in its talking animals' faces in the 1995 film Babe.

The complexity of the shots in the film, including elaborate sets such as the door vault, required more computing power to render than any of Pixar's earlier efforts combined.

[35] In October 2000, a teaser trailer of Monsters, Inc. was unveiled, which could not only be found online, but was also attached to the home video releases of Toy Story 2.

It was even the fourth film of the year to reach $60 million within its first three days of release, just after The Mummy Returns, Planet of the Apes, and Rush Hour 2.

It finally reached $74,437,612, standing as 2001's third highest-grossing film and the third largest U.S. animated feature of all time in the country behind Toy Story 3 and Finding Nemo.

The website's critical consensus reads, "Clever, funny, and delightful to look at, Monsters, Inc. delivers another resounding example of how Pixar elevated the bar for modern all-ages animation.

[70] Charles Taylor of Salon magazine stated, "[i]t's agreeable and often funny, and adults who take their kids to see it might be surprised to find themselves having a pretty good time.

[74] Roger Ebert of the Chicago Sun-Times gave the film 3 out of 4 stars, calling it "cheerful, high-energy fun, and like the other Pixar movies, has a running supply of gags and references aimed at grownups".

[77][35] At the Kid's Choice Awards in 2002, it was nominated for "Favorite Voice in an Animated Movie" for Billy Crystal (who lost to Eddie Murphy in Shrek).

[35] Shortly before the film's release, Pixar was sued by children's songwriter Lori Madrid of Wyoming, stating that the company had stolen her ideas from her 1997 poem "There's a Boy in My Closet".

Madrid mailed her poem to six publishers in October 1999, notably Chronicle Books, before turning it into a local stage musical in August 2001.

Her lawyer asked the court to issue a preliminary injunction, that would forbid Pixar and Disney from releasing the film while the suit was pending.

[80] In November 2002, Stanley Mouse filed a lawsuit in which he alleged that the characters of Mike and Sulley were based on drawings of Excuse My Dust, a film that he had tried to sell to Hollywood in 1998.

John Goodman, Billy Crystal, and Steve Buscemi reprised their roles of Sulley, Mike, and Randall, while Dan Scanlon directed the film.

Laugh Floor opened at Walt Disney World Resort's Magic Kingdom in Lake Buena Vista, Florida, replacing The Timekeeper.

The show is improvisational in nature, and features the opportunity for Guests to interact with the monster comedians and submit jokes of their own via text message.

The storyline takes place after the movie and focuses on Sulley and Mike's daily struggles to operate Monsters Inc. on its new laughter-focused company policy.

In November 2017, Disney CEO Bob Iger spoke about plans to develop a television series spin-off of Monsters, Inc. among other properties owned by the company.