From the Super Mario Wiki
A Limbo Guy without its stick.
Limbo Guys are a species of Spear Guys that prefer to always play limbo with anyone who passes by. They live only on a small island near Yoshi's Island. While Dancing Spear Guys jump around, the invincible Limbo Guys come in color-coded pairs and "dance" with limbo sticks. They attack Yoshi by simply dancing around while trying to trip the Yoshi with their stick, and Yoshi must jump over them to avoid their attack.
Limbo Guys (as an enemy) only appear in Yoshi's Story, and only in Stage 5-3: Shy Guy Limbo. They also made a cameo appearance in both Mario Party and Mario Party 2.