INTP:
As a supposed engineering student, you might first imagine something as simple as a motor and a cam system. 2 DC motors with nubs on the shaft are all that are needed. The toys move very obviously like cars that are divided left side and right side wheel control.
The rest of you folks surprise me. Tsk.
That did cross my mind but I don't think it is so simple. I think the legs on one side must move as a single and as a pair so I suspect a minimum of 4 motors is needed.
...R