YMMV / Star Trek: The Next Generation S4 E11 "Data's Day"

• Harsher in Hindsight: Lt. Stiles's fears about Romulan spies being in the Federation turn out to be completely justified. Gets even worse in Star Trek: Picard, where the head of Starfleet Intelligence itself is a Romulan mole.
• Hilarious in Hindsight: Dr. Crusher says she doesn't want to be known as "The Dancing Doctor" again. Some time later, we have another Doctor dancing.
• Inferred Holocaust: The Romulans had a spy masquerading as an ambassador who gets away unscathed. Who knows what vital secrets she might have brought back? It is brought up in "The Drumhead" later that season.
• Magnificent Bastard: Subcommander Selok is a Romulan spy who poses as a Vulcan diplomat named T'Pel in the Federation and Admiral Mendak is secretly her commanding officer. Selok has been gathering intelligence and secrets within the Federation for years and when she needs to be extracted, Mendak contacts the Federation and claims to want to sign a peace treaty if "T'Pel" negotiates it. Picard meets Mendak in the Neutral Zone and he agrees to bring T'Pel aboard his ship to begin the peace talks. T'Pel is seemingly killed in a transporter accident, but in reality, Mendak sends a second transporter signal and beamed Selok aboard his ship, leaving fake remains in her place. Data discovers that remains are fake and Picard confronts Mendak, resulting in Mendak revealing that T'Pel is Selok and Mendak summons several other Romulan ships to force the Enterprise to retreat. Selok and Mendak are among the few adversaries to hand Picard a defeat.
• Signature Scene: Probably most famous for the sequence where Dr. Crusher teaches Data how to dance.
• The Woobie: Despite the happy ending, this Data’s day is not a lucky one for Miles O’Brien. Keiko has canceled their wedding and someone has apparently been killed in a transporter accident.

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