Every time I go to Artist & Craftsman supply in Baltimore (i.e., my happy place) I cannot resist buying a few of the $0.99 Safari Good Luck Minis. I now have a big clump of them on my desk. Ostensibly they are for reference, on the occasions I forget what frogs and cows look like, but they are also great for warm-up doodles.
As of now they have inspired the following series, all done while procrastinating on work with actual deadlines: