Thorn (Wario Land series)
From the Super Mario Wiki
Thorns are obstacles found in various environments throughout the Wario Land series. They come in various forms, inter alia as iron balls with pointy spikes, rotating thorns or electrical traps. The thing they all have in common is that they hurt Wario and haul him backwards if he touches them. Thorns cannot be destroyed by anything and thus have to be avoided.
Wario Land series
Thorns make an appearance in Wario Land II and are first seen in a level called Through the thorny maze!! in Maze Woods. Most levels that include these obstacles also feature the Owl, a helpful animal that carries Wario through the air. The thorns serve as obstacles in these passages, making navigation through the air more difficult. Thorns also reappear in Wario Land 3 where they serve the same purpose as in the previous game. In this game, they always have the same design, but the palette changes depending on the level and time of day.