Nidoo is a black blob with white eyes (green in Kirby: Triple Deluxe). It can take on the appearance of several objects -- these objects vary from game to game.
Kirby's Dream Land 3
Nidoo disguises itself as a door, and when Kirby comes close enough, it shows its true form and then bounces around. Nidoos can be distinguished from real doors by looking at their shade of color; Nidoos are always lighter colored than a normal door. Nidoo grants no Copy Ability when inhaled and looks as though it is made of Dark Matter, much like Mariel.
Kirby: Triple Deluxe
In Kirby: Triple Deluxe, Nidoo appears in certain haunted stages, such as Stage 4 of Lollipop Land and Stage 3 of Wild World. Nidoo's eye color is green in this game. Its behavior has changed since Kirby's Dream Land 3; it now tries to attack Kirby by slamming down on him when he tries to enter the door. Nidoo more commonly disguises itself, however, as a large platform. It will disappear shortly after Kirby sets foot on it, often dropping the hero into a pit or spikes.
A few Nidoos disguise themselves as paintings with doors drawn on them. If Kirby tries to enter the door, the Nidoo will reveal itself and slam down on him.
- In Kirby: Triple Deluxe, Nidoo's snicker sound effect is copied from Sphere Doomer's snicker in Kirby's Return to Dream Land.