In the Tamil dubbing episodes, Lady Rainicorn speaks in Malayalam (a language similar to Tamil), so the viewer can sometimes understand whats she's speaking. In one room of the Princess Bubblegum's castle, there are two pictures of Lady Rainicorn on the wall; one of her upper half, and one of her lower half. read more
Actually, the answer is super simple. The voice actor is a Korean person: Niki Yang - Wikipedia, so when they needed Lady Rainicorn to speak a foreign language, it was just easier to pick the one that she already knew. read more
I would think she has much more stuff to take care of, rather than watching adventure time. Maybe at night when she's relaxing and resting but still probably not. read more