From the Super Mario Wiki
A Sad Goomba is an enemy found on Vibe Island during the events of Super Princess Peach. Sad Goombas are blue, and are always seen sitting around and crying. When Princess Peach approaches them, they immediately get up and charge at her. According to the game's Glossary, it "Attacks when it's sad so you feel bad attacking." The Mad Goomba is the opposite of the Sad Goomba and is red instead of blue. Due to its coloring, the Sad Goomba is similar. There is also a flying sub-species of the Sad Goomba called the Sad Paragoomba.