From the Super Mario Wiki
A Hot Foot (plural: Hot Foots or Hot Feet) is a Lava Bubble-like creature that inhabits the candles in the fortresses of Super Mario Bros. 3. Their behavior is similar to Boos. If Mario or Luigi looks at one it will stand still. If Mario or Luigi look away it will resume walking towards them. Hot Foot can only be defeated by throwing a hammer at it as Hammer Mario or being invincible while touching it.
The Adventures of Super Mario Bros. 3
A single Hot Foot makes an appearance in The Adventures of Super Mario Bros. 3, in the episode "Princess Toadstool for President", where it leaps off of its candle and chases after Mario and Luigi for a brief time.
Nintendo Adventure Books
In the Nintendo Adventure Book Koopa Capers, a large number of Hot Feet appear guarding a coin-filled cave Luigi can find in the Magma Pits. After Luigi collects some of the coins, the Hot Feet will chase him, into either a Fire Chomp (leading to a Game Over) or a door leading to a chamber filled with Fire Snakes. Referencing the confusion over the plural version of their name, Luigi is unable to decide on whether or not to call them Hot Feet or Hot Foots.
Names in other languages