I knew I wanted to do the Chain Chomp today, but that didn’t take nearly as long as I thought it would, so I added in the Bullet Bill, the Missile Bill (which is the same sprite but flickers the color of their target), and the Pile Driver Micro Goomba, which I forgot to add in when I did the Goomba set earlier in the month. It’s just a Micro Goomba that’s been stuck in a block that jumps on the Marios, but still a pretty frequently-recurring enemy in Super Mario Bros. 3
Bullet Bills are from the first Super Mario Bros. game, and their return in SMB3 meant a bit of experimenting could be done with them. And thus we got the Missile Bill. While Bullet Bills are shot and travel in a straight line forever, Missile Bills can turn around and heat-seek the heroes, while glowing red if they’re hunting Mario, or green for Luigi. Missile Bills can’t change their altitude, just their horizontal direction, so they’re not TOO much more difficult to avoid, but still a fun addition.
And the Chain Chomp is literally modeled after an angry dog that Mario lead designer Shigeru Miyamoto had an experience with a child. It’s such a simple design, but these guys have appeared not only in several Mario games, but also The Legend of Zelda: A Link to the Past.