The first level they appear in is 2-1, making them one of the earliest enemies Mario ever fought. Mario can defeat a Sidestepper by jumping underneath them, causing the platform they are on to damage them. Two hits are required to defeat one. After one hit their face changes to a mad one. Later in the game a blue variety appears. If you fail to defeat a Sidestepper, they will turn green and move faster.
Other Mario games
Sidesteppers later appeared in Mario Clash. Two shell hits were required to defeat one.
They also appear in the remake of Mario Bros. that is included with the game, and later appears with all Mario Advance games.
In Mario Power Tennis the Sidesteppers appear on the Mario Classic Course alongside Shellcreeper, Fighter Fly and Freezie. In a Gimmick mode match, the enemies have the ability to trip players. They can be defeated by using the POW Block and walking into them, just as in Mario bros.
In Super Smash Bros. Brawl, Sidesteppers and Shellcreepers are found in the Mario Bros. stage. Due to the low ceilings, normal KOs are hard to get, so Sidesteppers and Shellcreepers are often used to do the dirty work.
When flipped over, Sidesteppers will get back up and change color, first to blue and later to purple.
The following is the trophy description from Brawl:
Crabby enemies taken on by Mario and Luigi. One bump from below wouldn't flip them over, but rather anger them so they moved faster. These pests had to be bumped twice before they could be upended and kicked off the stage. If left alone after being turned upside down, or if there was one left, their speed would increase. They went by the basic name of "crabs" in Japan.