As the character is going to be symmetrical, and looking straight ahead, draw half of the shape with the pen tool, then copy-&-paste it (Ctrl/Cmd+C, Ctrl/ Cmd+V). Next, reflect the copied shape by choosing Object > Transform > Reflect.
With the smart guides on (Ctrl/Cmd+U), drag the copied shape by the top anchor point using the Direct Selection tool to meet the same point on the original shape. Select both points by dragging over them and press Ctrl/Cmd+J. Select ‘smooth’ and click ‘OK’.
Now for the bumps. Using the ellipse tool, hold down Shift, and drag, making a circle the size you want each bumpy bit to be.
Copy-&-paste the circle, and position them around one half of the character from the top down, creating the bumpy effect. When you reach the last circle, select the bottom half of it and press Delete.
This will get rid of half of the circle and just tidies things up a bit. Open the pathfinder palette and, while holding down the Alt key, click Add To Shape Area. This closes the shape.
Select all the circles and copy, paste and reflect, as in step 3. Move your copied circles, so the top circle lies exactly on top of the original set. Delete the very top circle so you don’t have any overlapping. While one circle is selected, choose Select > Same > Fill Color, this will select all the circles and the rough shape underneath. Hold down Alt and click Add To Shape Area in the pathfinder palette. This will create one solid shape.
Next you need to add detail and features to the character. To make its mouth, use the ellipse tool to draw the size and shape you want. You can adjust the shape by clicking on individual anchor points, and use the cursor keys to move. Once you’re happy with the shape, make some teeth.