|This article's title is derived from Japanese|
|...because it was never localized to English in official sources.|
As implied by its name, the Waddle Dee Steel Fortress appears to be a tall, metallic fortress. It has a face with yellow eyes and a red circular mouth (which acts as a missile launcher). Segments of the tower are divided by bronze spiked bands. One of its segments consists of three logs that hold up the rest of the tower above it. Attached to the side of the missile-shooting segment is a small platform that holds three Waddle Dees.
Waddle Dee Steel Fortress appears at the end of Stage 5 of Old Odyssey and in Stage 8 of Royal Road. After Kirby inhales two of the Waddle Dees' homes, they leap off a cliff out of desperation. The pink puff runs over to the edge, and before his eyes, the Waddle Dee Steel Fortress rises up. It shifts up and down, firing a large missile at Kirby whenever it reaches his level.
It can be destroyed by inhaling a missile shot by the fortress and firing it back at its wooden legs three times. With each hit, the fortress will move faster. After the third leg is destroyed, the building will collapse and plunge the Waddle Dees into the pit below. The exit door then appears on the lower half of the destroyed fortress.
At Royal Road, the three Waddle Dees are instead Sectra Dees.
- The Waddle Dee Steel Fortress is part of a Kirby parody of the fairy tale, The Three Little Pigs, with Kirby taking the role of the big bad wolf and the Waddle Dees being the pigs. First, Kirby swallows a house made out of straw, from which the Waddle Dee inside runs away. Kirby then reaches and inhales a cabin made out of logs, from which two Waddle Dees run. Further ahead, there is no brick house, but the Waddle Dee Steel Fortress instead is seen.
- As the fortress' health becomes depleted, the Waddle Dees on the platform become more frantic, running around in circles by the time the fortress is defeated.
- It is unknown whether or not the Waddle Dees built the fortress, or if they are controlling it in some way.
- Of all the enemies that are defeated exclusively with the Hypernova ability, Waddle Dee Steel Fortress is one of the five that are treated like mid-bosses. The others are the Mowlee Bros., the Gigant Chicks, King Phanta, and the Winged Eggers.