Talk to your child about what you see. Describe colors, shapes and parts of the crab's body, pointing to each one as you say its name. Pause between sentences so the child can "answer" with babbles or gestures.
Feel the crab's shell. Hold the child's hand to help him/her stroke the shell and feel the smooth texture.
Press on the crab's back to flatten the toy against the playing surface.
Turn the crab onto its back and encourage the child to tap the legs to rock it back and forth.
Hide the toy behind a cloth or blanket to play peekaboo. ("Where is the crab? Peekaboo! Here it is!")