Seahorses

I have a friend who speaks English as a third or fourth language. He speaks very well, but on rare occasions he makes mistakes which can be hilarious, like in this story:

I was sitting at home, doing something on the computer. It was a hot day and I hadn't opened the window. He came in, clapped me on the back, and said, "It smells like seahorses in here!" I had no idea what he meant. He was as confused as I was that I didn't get it. We tried to figure out what me meant, then gave up.

Hours later, at dinner or something, he suddenly looked up from his phone and declared "OH! I meant hippopotamus!" He had recently been to the zoo and was trying to tell me I smelled bad.

So now, the gym is the seahorse workshop. Concert halls with smelly fans are seahorse castles. Smelly locations in general can be termed seahorse palaces.