Creating the main character in a story is the most important step for me when it comes to tackling the illustration. Until that character comes to life, I find it hard to think about anything else. Here are a few of the predecessors of Sam, from the book Sam's Big Secret written by Dr. Stephanie Margolese.
In the final book, we get to see Sam the turtle both in the standing position as well as in his shell when he is scared and hides there.
Maintaining the visual clues and resemblance for the character through multiple positions and changes is important because we want it to go seamlessly.
It was very important for this character to be able to show a range of expressions while still being friendly looking.