I started this off by reading funny moments on TVTropes. For some reason, they were all in the first few minutes of the episode. Anyway, this episode features Gumball saying that plants aren't important. Leslie (a plant) hears this and is offended. Gumball then tries to learn about plants. I guess the funniest bits probably are at the beginning. Gumball's exploits are the highlight here.
They try to get the other to do crazy things to show what they know about plants. I guess the plot isn't that great, but it's still hilarious. It's great we get to see the other characters appear too. It really is the side characters and their interactions that make this show so great. Gumball can be willing to satisfy other people. He's not a complete jerk. ****