From the Super Mario Wiki
Egg Pawns also appear in the Mario series, acting as obstacles in some of the Dream Events of Mario & Sonic at the Olympic Games and Mario & Sonic at the Olympic Winter Games. In the Wii version of Dream Race, two of them are walking in the middle of the circuits, blocking other players. When a player runs into them, at the slightest touch, they will explode, stunning the player for a second. This also greatly decreases their speed. After one has exploded, they are soon replaced after another lap is complete. They appear as targets in the DS-exclusive Dream Shooting, along with Kikis and Flappers.
In Winter Games, they appear in Dream Alpine, Dream Snowboard Cross, and Sonic's version of Dream Figure Skating. In the first two, they serve as obstacles. Unlike the first game, however, they do not explode on contact; they simply slow the player down without even noticing. In Dream Figure Skating, they appear in phase 2 of the Sonic world. Jumping at the specified time will cause the player to jump on it, defeating it. Sometimes, the player will jump on a Spring then jump on it.