Thought Bubbles are knowledge manifest. Extracted from the host brain through the nearest orifice, they are then orally ingested (to absorb the knowledge) or popped (to destroy it). Thoughts can be implanted, secrets distilled, memories eradicated.
1) To learn arcane knowledge from a rival wizard.
2) To make a loyal retainer out of a powerful foe.
3) To remove the memory of last night liaison with a less than comely bar wench.