Gregor's Greatest Invention is a 2001 short film (11 minutes) directed by Johannes Kiefer.
Gregor lives with his elderly, infirm grandma. They are very close and Gregor is happy to give Grandma the occasional leg massage or wheel her around in a wheelchair. Unfortunately, Grandma has three nosy, pushy friends who keep trying to strongarm Grandma into an old folks' home.
One day a wheelchair mishap causes Gregor to discover that Grandma, who is usually wheelchair-bound, can walk with ease in water due to water's buoyancy. Gregor, who is a tinkerer, fixes up a ceiling rig to give Grandma walking support, but that doesn't work out either. Finally Gregor comes up with an even more unusual idea.
- Backseat Driver: The three old ladies pester Gregor as he drives them, telling him to slow down or put the van in second gear as they go downhill. One snipes that he must have just passed his driver's test.
- Balloonacy: Two weather balloons get Gregor airborne. Just one weather balloon is enough to have Grandma skip-walking along the ground.
- Grumpy Old Man: Grumpy old women in the persons of Grandma's three friends, who are always complaining and take every opportunity to insult Gregor. As Gregor goes airborne thanks to the two balloons one of the old ladies says "Let him fly away!"
- Happy Ending: The buoyancy of a balloon has Grandma literally skipping along on the ground, as Gregor cheerfully hobbles along beside her, on a crutch after she shot him.
- Impairment Shot: Grandma whips out a rifle in order to save Gregor as he's flying away. He's terrified, and he's right to be, as shown by the Impairment Shot demonstrating Grandma's very poor vision. (Sure enough, she shoots him in the leg before she pops one of the balloons.)
- Significant Background Event: There must not be a parking brake on Grandma's wheelchair. As Gregor, in the foreground, stops to pee, Grandma and her wheelchair roll away out of frame. He doesn't find out what happened until she's already in the water.