"Oi, I like surprises!" Hickey points out, with an innocent little grin on his face that Billy knows is very much not innocent. "Don't see why others don't."

He can easily see why other people don't like surprises. Surprises are nice when they're fun, aggravating when they're not. And more often than not, they'll end up in the 'not' section of things. But it's him! And Billy's Billy! So obviously Billy should know that this is a fun surprise (like a ring) and should ignore all the times that there weren't fun surprises (like taking a shit on his bed).