Theres a 15"+ Oscar at my LFS and if you get within 8" of the tank, he tries to eat the glass, freaking out in aggression and panic. It's kind of upsetting. Its tank is overcrowded with silver dollars and its only 90g at the most.
My brothers Oscar acts like a dog. he only eats one pellet at time. (meaning, if you drop 20 pellets in there, he'll stare at you like you have to be joking. you can only drop in one pellet at a time) He beats the craps out of his tank mates, hates my brothers girlfriend, yet he loves to see my brother. He knows who cleans his water, turns out the lights, and gives him food. Very smart fish (sometimes)