From the Super Mario Wiki
Piro Dangles are
enemies from
Super Mario World 2: Yoshi's Island. They are wisps of fire that can never be defeated by the
Yoshis. Piro Dangles can only be found in a secret room in
Burt the Bashful's fort. These fire creatures simply travel around large blocks, and will hurt
Yellow Yoshi if the dinosaur touches one of them. The Piro Dangle looks very similar to another enemy from the
Mario series -
Spark from
Super Mario Bros. 2. In Super Mario Advance 3:Yoshi's Island, they reappear in
Endless World of Yoshis, and can now be obilerated with a
Ice Watermelon. Their faces seem similar to that of Fryguy.