It looks like we still don't know what happened to Andy's dad in "Toy Story." Theories have been floating around for years and figure Andy's parents are either divorced or his dad had died. According to Mike Mozart, who claims he serves as a "consultant" on "Toy Story," it's the latter.
Mozart says his friend and Joe Ranft, Pixar’s former head writer, shared with him the story of Andy's dad before he passed away in 2005 and it's a sad one. Andy's father, also named Andy, survived polio as a kid but ultimately died of Post-Polio Syndrome after fathering Andy Jr. decades later. As the theory goes, before Andy Sr. died, he gift his son Woody, Slinky, and Mr. Potato Head.
The problem with this theory? Andrew Stanton, who was a writer on all three "Toy Story" movies and is writing the upcoming fourth installment, says it's not true. "Complete and utter fake news," he tweets. "Everyone go back to your homes. Nothing to see here, folks." He then adds the hashtag #IWasThere.
Source: Andrew Stanton