The problem people have with "Car extends Vehicle" is that they expect magic. It's the same impatience we sometimes feel with little kids because they're not grasping something we've been taking for granted for decades. If you're trying to teach someone new to OOP, there is no example that will take them from their current level of knowledge to yours, in one fell swoop. You can't expect them to grapple with decisions such as "inheritance vs. delegation" when they're only now learning what inheritance is all about.
So yeah, "Car extends Vehicle" and "Duck extends Bird" works pretty well at that point. You can try to cram "Penguin" and "Helicopter" and "Flyer" and "Vehicle" down your students' throats in the same lesson, but I doubt that will magically make them digest it properly. And if you can't do that with easy stuff like "Duck" and "Bird", how do you expect them to swallow "NumericHalo" and "ImageDisplay"?
So yeah, "Car extends Vehicle" and "Duck extends Bird" works pretty well at that point. You can try to cram "Penguin" and "Helicopter" and "Flyer" and "Vehicle" down your students' throats in the same lesson, but I doubt that will magically make them digest it properly. And if you can't do that with easy stuff like "Duck" and "Bird", how do you expect them to swallow "NumericHalo" and "ImageDisplay"?