The base head and body are from a Lion Brand pattern (
http://www.lionbrand.com/patterns/81030AD.html?noImages=) worked with only one strand of yarn. I tried an earlier bunny with two strands held together, and it was just a complete pain. It'll be small, but you can add rows in the middle (which means you'll be adding rows once you start decreasing). They're also pretty quick to make.
I didn't sew the head together until the face/cheeks were done. The face is a bit of black yarn, and two French knots for the eyes.
For the cheeks I used a smaller hook (either a G or an F). They don't take long to make, so it might be good to make one and see if it looks right.
Round 1: ch 2, work 6 sc in the second ch from the hook
Round 2: sc in the first stitch, two sc in the next stitch until you get 12
For the ears:
Ch 2, 6 sc in the second ch from the hook
I meant to keep track, but ended up just doing 6 sc around until it looked right (yeah, that's how most of my patterns end up). Based on some pictures, Pikachu's ears get a bit wider, but it didn't look right on the doll.
Hope that helps!