When Lucifer picks up the red apple and says "Hello, old friend," he is referring to the forbidden fruit Adam and Eve ate in the biblical Garden of Eden, apocryphally called an apple (the Bible never specifies a kind of fruit).
In his nightclub, Lucifer begins a song on the piano. Decker walks over and feels his torso to see if he is wearing a bulletproof vest. The song he is playing on the piano is "King of Pain" by The Police. The lyric, "It's my destiny to be the king of pain" is featured in the song comparing different things to his soul. The song was released in 1983 on their album Synchronicity.
The episode contains one of the few instances in which someone is able to resist Lucifer's compulsion, though not easily.
The title is said by Lucifer.