Just found an alternative Necron history I wrote 18 months ago and I thought I'd share with everyone...
Disclaimer: This was written way before any of the new models were around, so try to remember what the old ones look like. Oh, it's supposed to be funny too
Background Theory:
In a parallel universe the machines rule the known galaxy. Their supreme commander, a guy called Skye Knett, decides that the best way to do away with his enemies is to send expert assassin drones back through time to kill his enemies as children.
However, Skye Knett never studied quantum physics when he was a little 386, and missed the vague theory regarding the Young's Slits experiment and parallel universes... When the Time-Environment Relocator and Mass Inertia Expander (or TERMIE for short) was completed, Skye dutifully sent a drone back in time and waited. Nothing happened. So he sent another. And another, and another and another and another and another and another (you get the picture) - he was a transistor short of a chip when it came to common sense.
Unbeknownst to Skye Knett, his TERMIE machine was shifting his drones through quantum space to one of the many parallel universes - the 40K universe. Unfortunately, the trip had a severe effect on the drones. Thier mission parameters had become ionised, so they thought everyone was thier target, and thier speech boxes became stuck in a cascade loop, so every word they said came out as a buzzing sound, best described as sounding like the word "Knneeeee-kkkroonnnnnn (click)". Hence the new name Necrons. BUT worst of all - the drones jaws had become frozen in a 'Bobo the clown' expression - inanely happy, but with anger hiding beneath that funny exterior.
So this is how the Necron incursion into the Imperium of man came to be. Drones who got deep fried, and a 386 who couldn't pay attention in quantum theory classes. But when you've sat through one yourself, you take pity on the machine named Syke Knett.