Pixar's 2009 movie Up is about an old man who ties balloons to his house and sails off for adventure. That was the basic premise, but the team behind the film knew they had to justify it with a backstory. Why would a grumpy old man decide to just take off? Where did he think he was going? And why use balloons? The answers to all those questions are in Ellie, who wasn't there but gave us all the reasons Carl did what he did. So they devised his life story, jammed into the first ten minutes of the movie. First there was the beginning, when he and Ellie met as children.
Then they condense Carl and Ellie's marriage into a four-minute montage with no dialogue, but an awful lot of feeling. Ask any adult, and they'll tell you this is the most memorable part of the movie. Maybe not so much for kids.
Director Pete Docter said they had 30 to 40 minutes of material that they whittled down to a ten-minute intro. Read the nuts and bolts of how the emotional rollercoaster of an intro was created for Up in an article at The Ringer. -via Metafilter