Ale Abreu wasn't confident about his animated film "Boy and the World" after screening it for an audience for the first time. The imaginative parable about a stick figure's search for his father left viewers feeling sad.

"I realized it wasn't the film I had expected to make," the Brazilian filmmaker said through a translator at the motion picture academy's headquarters. "The solution was to change one scene."

It worked. "Boy and the World" is among the five nominees up for the animated feature film Academy Award on Sunday. Abreu and the other nominees shared their fears of working in the fragile medium during an event Thursday celebrating their creations.

"Inside Out" filmmakers Peter Docter and Jonas Rivera noted there was originally concern children wouldn't understand the concept for their Pixar flick about a team of personified emotions working together inside a young girl's noggin.

"In the end, we had to simplify the film for the executives, but the kids loved it," joked Docter.

The creators of "Anomalisa" said constructing the film's stop-motion sex scene was one of the biggest challenges of bringing writer-director Charlie Kaufman's script originally written as a radio play to life with puppets.

"That scene took the longest," said director Duke Johnson. "It took six months to animate. We didn't know actually until we screened the film if it worked."

Other nominees vying for the animated feature film trophy at Sunday's 88th annual Academy Awards include the Japanese adaptation "When Marine Was There" and the stop-motion comedy "Shaun the Sheep Movie." The category was first introduced at the 2002 ceremony with "Shrek" winning the inaugural trophy. Despite the more emotional of this year's animated nominees, none cracked the best picture category for a spot alongside the likes of "Spotlight," "The Big Short" and "The Revenant."