Idea 1 -
In a post-apocalyptic setting, a tiny police robot that was built by Humans still roams around the streets and buildings upholding the law, flinching and investigating anything that moves, rolling around with it's sirens going in the hope that he will at least find something to interact with. the story ends with a large building buckling under it's own weight and opening up a new passage-way, it's a police station and as he ventures inside he finds another Police robot, dormant. He checks to see if it'll turn on, after a sort pause, the robot turns on and the animation ends.
A secret life of a house robot. Set in the future this animation would be about a servant robot that has the run of the house while the owner is away and is a seemingly emotionless robot when they're home. The animation would feature the robot getting up to all kinds of acts that you wouldn't expect a robot to do; like watch TV, play games, smash things, run around, going to the toilet maybe even inviting friend robots round... then cleaning up his mess and acting 'normal' for when they come back home.
Set in a post-apocalyptic, futuristic building site. An industrial crane robot is set up beside a museum of art to help with the building work. because of the lack of human interaction, it finds it'self admiring the artwork of the building. The wanna-be creative robot wants to create art but with every form of art he tries, he's 'unsuccessful'. in one attempt, it accidentally knocks down a wall of the museum... artwork is revealed to him that largely resembles his own work and gives him a sense of achievement and a drive to create more.
My personal favorite from the bunch is Idea 1, I feel like it's got a nice story arch and i feel like it could be a really cute animation if done correctly.