A sequel to Statistical Probabilities (1997). Since the plotline revolves around Sarina, who was catatonic in the previous episode, the producers weren't sure if she could handle an episode where she must talk and carry a lot of the story. So they took the unusual step of having her audition for a part she had already played. According to the producers, "the role was hers to lose, but within seconds, we knew she was in."
When the savants are helping Sarina regain a normal speaking voice by having her do standard singing scales that vocalists use to warm up their voices, Tim Ransom (Jack) asks her "Are you tone-deaf?". This was something of an inside joke, as Tim Ransom is tone-deaf in real-life, whereas [link=nm0758276, Hilary Shepard, and Michael Keenan all have wonderful singing voices. Hilary Shepard was even the singer for a punk band in the late '80's.
The episode is heavily influenced by the movie Charly (1968) based on the sci-fi novel "Flowers For Algernon" by Daniel Keyes, which explores very similar themes.
O'Brien says at one point "I can't break the laws of physics." This paraphrases Star Trek (1966)'s Scotty's famous line "I cannae change the laws of physics."