What is the name of the short film that preceded Up?

The short film that preceded Up is Partly Cloudy.

Pixar released Partly Cloudy as the theatrical short shown before Up in 2009. Written and directed by Peter Sohn and produced by Kevin Reher, it imagines clouds as friendly creators of babies, while storks deliver those babies to families. The story centers on Gus, a gray cloud whose unusual creations make his stork partner's job increasingly difficult.

The short grew from Sohn's childhood question about where baby animals came from after watching Dumbo, in which a stork delivers the title character. Partly Cloudy runs for about 5 minutes and 45 seconds and was later included as a bonus feature on Up's DVD and Blu-ray releases.

A common mix-up is choosing another Pixar short associated with a feature film. Lifted preceded Ratatouille, Presto preceded WALL-E, and For the Birds preceded Monsters, Inc. Partly Cloudy is the specific theatrical companion to Up, not a scene or deleted segment from the feature.