Ha ha! yes! I keep telling @Ham that I'm only good at catching Green Sunfish...the World's Easiest Fish to Catch.
Absolutely, the ones with unique color patterns and scale patterns are definitely easy to recognize when I/we catch them again. The solid ones are a bit tougher, since there are multiple ones that are solid white, or solid yellow, or solid orange, etc. But even some of those might have longer fins, or slightly more/less colored fins. Its actually kind of fun to go through the pictures and try to match up ones I've caught before. Really cool fish.
At the beginning of the day, the fish were pretty aggressive, and catching seemed easy. One passerby stood next to me for a bit, asking if there were bass in the pond. (No bass, and I told him so.) I saw a colorful Koi out in open water. I cast out ahead of it, and it immediately swam up to the fly from below, acting really aggressive. Bam! Fish on! It looked so easy! The guy HAD to have been impressed, right? I was. But he just mumbled "I bet there's bass in here," and wandered off. Soon enough, the fish got spooked or something, and the rest of the outing was a lot more work to find some willing to strike.