Rob Turpin's A Droid a Day project is all about proving that you just can't get tired of robots. Since August 2013, he has been posting droid doodles every. single. day. Most robots are captioned with a name or title that is descriptive of their function, which adds a touch of personality.
I stalked his blog a little bit and found that he started doodling with pen and pencil more often to stop himself from putting more thought into drawing something that looks nice rather than capturing a great idea. "Throwing in a really broad shape with the markers makes you forget about trying to create something beautiful, it’s about creating a cool shape, or an interesting form." Wise advice for doodlers!
Be sure to follow his blog for tons of valuable insight. I especially like it when he shares his illustration process from initial sketch to final color.