Hi, everyone! I'm relatively new to the fandom and very new to this community. Maybe my bunnies should come with a warning label as far as n00bishness goes, but I hope someone will enjoy them.
1.)[Any universe] Ratchet and a Decepticon [choice is the writer's] somehow wind up as the last two Cybertronians in the universe--whether because of the war, a widespread disaster, or some such event which would leave the Decepticon damaged. Guess who repairs him, out of nothing but a fear of being alone? The relationship that follows can be romantic or non.
2.) [Animated] It has been hinted that Prowl never completed his ninja training. This is because he was kicked out of the "dojo" which trained him [also explaining how he wound up on cleanup duty] for unknown reasons. Jazz takes it upon himself to complete Prowl's education, acting as a mentor in both the art of Metallikato and relaxation.
3.) [2007 movie AU] When Optimus Prime comes to Earth, he finds the AllSpark not in the possession of humans, but in that of a barely-sentient clean-up bot named WALL-E who thinks it's a giant Rubik's cube.