My dad's goldfish

My dad owns a small fish tank in the living room with two goldfishes in it.  But one day, we woke up to find this:  

To many of you guys who have owned fishes, you know that a fish upside down floating on top usually means a dead fish.  (Regardless of what the waiter at the Chinese restaurant tells you, the fishes on their backs either dying or already dead.)  But to our surprise, when we gathered the net and prepared to 'fish' him out (excuse the pun), he started swimming around like nothing was wrong.  We later sprinkled food in there, and he ate like normal as well.

Fast forward 2 months, and this is him now:

We realized he only moves when he sees moving people near him, obviously equating movement with food, making him either very smart or extremely lazy.  Probably both....