The Saddest Little Robot - Brian Gage, 2003.
The main character is Snoot, a Drudgebot working in Dome City. (Already it's hard to get past the names.) Snoot is different from the other Drudgebots--he's funny-looking and too curious, so he gets a hard time from everyone. Drudgebots are the bottom rung, under Guardbots and Halobots, all under the guidance of Father Screen, who leads the chorus of "Happy Robots Produce Happy Fruit!" There's a tribute to Karel Capek in RUR, the role model, most-productive robot. Robots are supposed to be delighted with their jobs, refrain from asking questions, and never leave the dome. Outside the scary Gremborgs lie in wait and there's no lifegiving light. It's a retread of We, 1984, Brave New World, and the whole dystopic genre. Guess what? Snoot leaves the dome! And guess what? What Father Screen has been saying about the Gremborgs isn't true!
The Dome is on an asteroid, we were told at the very beginning, so it can't have an atmosphere; yet Snoot not only meets two fireflies, Tik and Tak (deeply annoying characters who speak in rhyme), but also a wise old caterpillar who lives in an apple tree. And you'll never guess what happens to the caterpillar at the end of the book!