Sally Impossible's ears do not change in color or appearance when her skin turns invisible.
When Rusty releases Cody from his chamber Cody is wearing an Impossible suit which is visible through his flames. Later when Cody and Ben subdue Richard Impossible only his gloves are visible through the flames.
While Professor Impossible is talking to Dr. Venture before he drops him off to die in the freezing cold, Prof. Impossible holds a pipe in his right hand. He then puts the pipe in his mouth and touches Dr. Venture's shoulder. When the camera changes angles, the pipe is back on his right hand and off Venture's shoulder.