Oh, dear.
In the reference photos (or using whatever reference you prefer), the rabbit head shape is triangular when viewed from the front, and oval like an American football when viewed from the side. At no angle is the head square.
On a real rabbit the ridge between the eyes is both wide and tall, making it difficult to see both eyes at once. This requires a cheat, because seeing both eyes is important to the character.
Also, curves are more cute than edges and angles.
1.
The red lines at the top and bottom are the top and bottom of the original head to make sure I got the scale correct.
I started with the eyes to make sure they were visible. One very large eye and one large eye turned to the side somewhat. Per the references, rabbit eyes are the same sort of shape as people eyes and the shape also reinforces the oval of the head.
Then the nose sitting between them. Diamond or triangle shape works.
Then the cheek line. The trick to the rabbit mouth that makes it look different than a cat mouth is that the rabbit mount goes rather far out and then back in towards the eyes. The cat has a stronger jaw and the mouth would go out less and then just angle back. This took a bit to figure out.
Finally the head lines. The rabbit head is very pinched at the top.
The squiggle on the left is notional for the back of the head area, which will get covered by the ears anyway. So it's just a squiggle.
If you look at these lines, even without the ears, I think it looks kinda like a rabbit.
2.
Pasted this onto the existing body. The dark line on the left is part of the original ear line.
Added ears. Real rabbit ears attach farther back on the head (per the references), but I kept the same style you had in the original. Might be too much like puppy ears?
Closed the gaps in the outer lines and filled with color.
Erased the noisy fur on the belly because I don't think it added anything.
Made the feet a bit bigger.
Colored in the features. Plenty of tweaking.
3.
Added more to the robot eye.
Between the first two images I moved the skull line one pixel further out. On the third I moved it back. It could still use a little fine tuning.
Eh, good enough.
Note the cheat for the ridge between the eyes. Using the lightest color to suggest a raised area from nose to crown.
The highlight on the belly might suggest Bugs Bunny a bit. Or maybe it's just ugly pillow shading.
Things left out:
I think the ears might work better if they were up instead of down, but I didn't know how much room you have for the character.
For me the main difference is to train the eyes to look at shapes and see what is really there. The brain often just makes things up, so instead of a rabbit that looks like a rabbit, you get a rabbit that looks like a stuffed animal.
Hope this helps,
Tourist
