Wisp

The Wisp is an enemy which is similar to the Blue Bubble; it will jinx Link if it touches him, however it is non-agressive and will simply float around. The sword does not affect them but the Gust Jar can be useful.

Quote from The Legend of Zelda: The Minish Cap Wisp figurine: "Appear in dungeons. They float in midair. They won't hurt you if you touch them, you won't be able to use your sword for a while."