Part -1:
You should perform all computations of the incision in the Robotics Toolbox and animate your robot performing the task using the SL3D Animation Toolbox. qYou should add Nathan to the scene. As hot dogs do not bleed, there is no reason to add blood to the incision.
You can learn how to add a cylinder to a MATLAB figure. This may require that you put the plotting in a loop rather than use the vectorization available with seriallink.plot().
Part -2:
Model Brat as a cylinder with 20 vertices around his waist and define the transformation matrix for each vertex that keeps the approach of the knife normal to the circumference and oriented toward the cut, and makes the cut 1 cm deep.