Question: Who produced the movie in which Wallace Shawn voiced Rex?

Context paragraphs:
Toy Story of Terror!: Toy Story of Terror!  is a 21-minute Halloween television special, based on the Disney Pixar "Toy Story" movies.  It is set shortly after the events of "Toy Story 3" and "Toy Story Toons", and premiered on the American television network ABC on Wednesday, October 16, 2013.  It was written and directed by Angus MacLane, produced by Galyn Susman, with Tom Hanks, Tim Allen, Joan Cusack, Don Rickles, Wallace Shawn, Timothy Dalton, and Kristen Schaal reprising their roles of Woody, Buzz Lightyear, Jessie, Mr. Potato Head, Rex, Mr. Pricklepants, and Trixie with Carl Weathers as Combat Carl and Stephen Tobolowsky as the motel manager.  Michael Giacchino composed the music for the special.  The film's soundtrack was released on October 15, 2013, on Amazon.com and iTunes in digital format.

Toy Story That Time Forgot: Toy Story That Time Forgot is a Christmas-themed 22-minute television special that aired on ABC on Tuesday, December 2, 2014.  It was written and directed by Steve Purcell and produced by Galyn Susman.  Michael Giacchino composed the music for the special.  Most of the regular cast from the "Toy Story" series reprised their roles, including Tom Hanks as Woody, Tim Allen as Buzz Lightyear, Kristen Schaal as Trixie, Wallace Shawn as Rex, Timothy Dalton as Mr. Pricklepants, Don Rickles as Mr. Potato Head, and Joan Cusack as Jessie, with Kevin McKidd and Emma Hudak joining as new characters Reptillus Maximus and Angel Kitty, respectively.  It was Don Rickles' final role before his death in April 2017.  The film was generally well received and even got a rare 100% rating on Rotten Tomatoes.

Christmas at Cartwright's: Christmas at Cartwright's is a 2014 American-Canadian romance television film directed by Graeme Campbell and starring Alicia Witt, Gabriel Hogan and Wallace Shawn Written by Margaret Oberman, the film is about a single mom who gets a holiday job as a department store Santa to pay her rent.  An angel Wallace Shawn enters her life and brings about some positive changes, including the spark of a new romance.  The film premiered on the Hallmark Channel on December 7, 2014.

Nice Girls Don't Explode: Nice Girls Don't Explode is a 1987 independently made American comedy film produced by Douglas Curtis, directed by Chuck Martinez, and starring Barbara Harris, Michelle Meyrink, William O'Leary, Wallace Shawn, and James Nardini.  The film was released by New World Pictures.

Toy Story (franchise): Toy Story is a computer animated film series and Disney media franchise that began with the original 1995 film, "Toy Story", produced by Pixar Animation Studios and released by Walt Disney Pictures.  The franchise is based on the anthropomorphic concept that all toys, unknown to humans, are secretly alive, and the films focus on a diverse group of toys that feature a classic cowboy, Sheriff Woody, and modern spaceman, Buzz Lightyear.  The group unexpectedly embark on adventures that challenge and change them.

Noah (1998 film): Disney's Noah is a 1998 television film directed by Ken Kwapis.  The movie premiered on October 11, 1998 and stars Tony Danza as a modern-day jaded contractor who undergoes a remarkable transformation while building an ark like Noah's.  It also stars Wallace Shawn and Jane Sibbett.

Wallace Shawn: Wallace Michael Shawn (born November 12, 1943) is an American actor, voice actor, playwright, essayist and comedian.  His film roles have included those of Wally Shawn in the Louis Malle-directed comedy-drama "My Dinner with Andre" (1981), Vizzini in "The Princess Bride" (1987), Ezra in "The Haunted Mansion", providing the voice of Rex in the "Toy Story" franchise, providing the voice of Gilbert Huph in "The Incredibles" (2004), and providing the voice of Calico in "" (2010).  He also starred in a variety of television series, including "Gossip Girl" and recurring appearances as Grand Nagus Zek in "" (1993–99).

My Dinner with Andre: My Dinner with Andre is a 1981 American comedy-drama film directed by Louis Malle, and written by and starring Andre Gregory and Wallace Shawn.  The actors play fictionalized versions of themselves sharing a conversation at Café des Artistes in Manhattan.  The film's dialogue covers such things as experimental theatre, the nature of theatre, and the nature of life, and contrasts Shawn's modest humanism with Gregory's spiritual experiences.

The Fever (2004 film): The Fever is a 2004 psychological drama television film produced by HBO Films, directed by Carlo Gabriel Nero and based on the 1990 play of the same name by writer/actor, Wallace Shawn.

Sibling Rivalry (Family Guy): "Sibling Rivalry" is the 22nd episode of the fourth season of the animated comedy series "Family Guy".  It originally aired on Fox in the United States on March 26, 2006.  The episode follows Stewie as he battles with his half-brother, Bertram (voiced by Wallace Shawn), who is born to two lesbians after Peter donates sperm.  Meanwhile, Lois begins excessive eating after Peter undergoes a vasectomy and loses his interest in sex.

Supporting paragraphs: Wallace Shawn Toy Story (franchise)
Answer: Pixar Animation Studios