How did we not know?

I recently watched the reality show, Top Chef, for the first time. The episode involved chefs making food based on the tastes of animals from the Chicago zoo. For example, the chefs assigned to make food based on the tastes of Gorillas baked banana bread. (But nothing on Top Chef is as simple as banana bread. I believe the bread had an assortment of fruits and glazes on top.)

One chef-group made appetizers based on penguin's tastes. They were given a list of food they could use which was mostly varieties of fish.

Several of us were watching the show. The spotlight was on the penguin table and I noticed one of the dishes. The judges were exclaiming over the chef's great job with the anchovies as the camera zoomed disturbingly close to a white rectangle of something topped with a small, silver fish.

"Where are the anchovies?" I asked.

"It's on top," acquaintance 1 told me.

"But that's a little fish on top." I argued.

"That's what anchovies are. fish." Acquaintance 2 explained.

"Isn't it some kind of olive? Y'know, how Garfield the comic cat always says something about anchovies and pizza? And most people don't like olives on pizza..." I stopped talking.

Acquaintance 1 and 2 were incredulous. "You thought anchovies were olives!"

JE looked confused. "I didn't know they were fish."

How did we not know? And why would anyone every put fish on pizza.