Thundersub is probably the most original idea yet. Of course, every cartoon has to have a base idea, and that idea is pretty much the same as everything else around here. Aliens, coming to Earth, taking over the world. Funny that these aliens (again) look so much like us, but these cartoons were made in the late 80's beginning of the 90's, so the movie Independence Day wasn't actually known yet. 

But the good side, doesn't have space ships to blast the Aliens to kingdom come, but a submarine! Yes folks, a submarine. This submarine is no little submarine at that. With the size of twenty football fields (the same size as a small norwegian city) is the actual size of this submarine. So this is no little dittie. 
I'm not going to say much about this cartoon, except that this cartoon has some excellent theme music, superb storyline, and a tromendous ending: 
In the end, they have to rebuild Earth's last hope into a spaceship to counter attack the aliens.. hmmmm... :)