The Old Series Finale Trick! This is the last episode of the original series, screening just four months and 3 days short of the 5th anniversary of the airing of the pilot episode "Mr. Big" on September 18, 1965.
The name of the episode's "MacGuffin", the stolen weapon, inexplicably changes from Narco 5-12 to Marco 5-12 in the second half.
The title refers to the 1967 Swedish film I Am Curious (Yellow), companion to 1968's I Am Curious (Blue), yellow and blue being the colors of the Swedish flag.
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