IIRC, it's the Marge's fear of flying episode.
Homer is banned from Moe's bar after unscrewing the cap of a sugar shaker, after Lenny and Carl do far worse things to him. After a week or so without going to a bar, he goes in search of a new watering hole, and first goes to a bar in a bad part of town and that is where the dirty mug exchange occurs.
Next is a "walking" scene suggestion Homer's fruitless efforts to find a decent bar. Other specific scenes include the Cheers bar, and Homer's exact double ("Guy Incognito") getting thrown out of Moe's bar.
Eventually, he goes to "The Black Box", a bar for pilots. The bartender asks where Homer's pilot uniform is. He says he "stored it in the overhead compartment". He is given a spare uniform and served the beer he craves. Someone bursts in and asks if anyone can fly to the Windy City (Chicago). When told that conditions are a little windy, everyone steps back except Homer, who is then put on a plane and expected to fly. He fiddles with the controls trying to figure out how to take off, and ends up retracting the landing gear on the tarmac, wrecking the plane.
The next scene shows a representitive of "Laughing Clown Airlines" telling Homer that if word of the incident got out, they would be "the laughing stock of the industry". In exchange for his silence, he is given free airfare to anywhere but Alaska or Hawaii.
So the familiy is on the plane, ready to take off, when Marge's fear of flying kicks in and she flips out, running up and down the aisle shouting "Let me off let me off let me off let me off let me off".
The rest of the episode centers around Marge's psychiatric treatment, and Homer's paranoia relating to it.
Facebook
Twitter