The working title of this episode was "All Apologies".
All Apologies is a song by
Nirvana, released in 1993 on the album
In Utero. In the original script,
All Apologies was supposed to be used during the closing montage scene and another Nirvana song,
Come As You Are, was to be used during the opening scenes. It's likely that the producers weren't able to get the songs' rights to use in the episode.
Eventually,
5-1: Thrill Kill only featured Nirvana songs but reverses those two songs;
All Apologies plays during the opening scenes and
Come As You Are plays during the end scenes.