The episode: “Fire Maidens of Outer Space,” ep. 416
The riff: Exclaimed by Joel as a military guy leans in over the head of one of his subordinates manning the Scientific Whatever Device.
The explanation: At first look, this just appears to be the typical sort of context joke they always make, and not an actual pop culture reference–but it is! As it turns out, there was actually a brand of shampoo in the 1970s called “Gee, Your Hair Smells Terrific.” That’s literally what was printed on the bottles. It’s no longer available in the States, but apparently remains popular in The Philippines. The unusual name was even satirized on “The Simpsons,” where a sports dome was named “The Gee Your Hair Smells Terrific Arena.”
Novelty factor: No way in hell I knew this one beforehand. Does anyone in the peanut gallery actually remember using “Gee, Your Hair Smells Terrific”? Also, look at this apparently Spanish-language commercial I found for it. It’s the only real commercial I could find on YouTube.