[Spike blinks. He wasn’t expecting that. Although, since it seemed that only ponies had cutie marks, he supposed creatures from other worlds had other things that would be considered pretty normal for them.]

“A stone? In your forehead? That sounds really painful. What does it do? Is it like a jewel? Because if it was a jewel, that would be torture!

[Spike is thinking about how horrible it would be having a jewel on your body that you couldn’t eat!]

“Why do only you have it?”