Lexonite

Lexonite is a perculiar radioactive mineral that appeared the two-part episode, "WordGirl Makes a Mistake". In it's solid, rocky form, it's a bright red that pulses and fluctuates with a softly glowing light. It has a rough texture and comes, accordingly, from Lexicon, WordGirl's home planet.

In the episode "WordGirl Makes a Mistake," a large chunk of Lexonite falls to Earth, coincidentially during an encounter between WordGirl and Mr. Big. WordGirl immediately begins to feel the negative effects that the mineral has over her - it eliminates all of her supernatural superpowers - flying and the like - and even cuts on her immense vocabulary so she misuses and mispronounces words, like "parsculiar". Later on in the episode the Lexonite is made into a star-shaped collar and into a large cage. It is unknown what happened to the mass quantities afterward.

Notably, Lexonite is a parody of Kryptonite, even mentioned by Leslie in the regard that superheroes are vulnerable from minerals that come from their home planet.

Interestingly, the Lexonite appears to have no effect on Captain Huggyface, possibly even insinuating he's not from the planet Lexicon.