George and A.J. (4:05)
IMDb; Pixar; Pixar Wiki; Wikipedia
streaming sites: Disney+; YouTube

This short was released in 2009 on iTunes as a bonus feature with the movie Up, to which the short is related. It was later released on other websites, and then on the Pixar Short Films Collection, volume 2, in 2012. (That's where I first saw it, but it wasn't until years later.) It's not so much an animated film as a storyboard animatic. So I think it's probably the only Pixar short that isn't CGI.

Two nurses from Shady Oaks retirement home, George and A.J., go to Carl Fredricksen's house to bring him to Shady Oaks. Instead, he flies away in his house, to which he has attached a bunch of helium-filled balloons. Subsequently, all the other senior citizens George and A.J. try to pick up follow Carl's example, in all sorts of improbable ways. Poor George and A.J. are completely at a loss for what to do (and their van repeatedly takes quite a beating from the fleeing houses). In the end, Carl returns home in a blimp, accompanied by his new friends (as seen in the movie). It's a pretty cute and amusing and imaginative short film.