For those not knowing the term, it's when a viewer is poking around in the 'fridge after a movie or show, then suddenly thinks, "Hey! How did Sydney Barstow get from Hungary to Melbourne, to L.A. all in less than 24 hours?" TV Tropes In other words, a plot inconsistency overlooked at the time, but noticed later. In my case, it's about eighteen months later so I might not be the brightest bulb in the pack.
In City of Walls and Secrets the Gaang hopes to sneak in with the crowd at Bosco's party but Toph nixes the idea, saying they don't know how to act in upper class society. "I learned proper society behavior and chose to leave it." she explains when Katara points out she doesn't exactly exemplify upper class breeding herself. This is where I find myself looking at the inside of the refrigerator door in bewilderment.
Toph's parents kept her existence a secret -- nobody in Gaoling knew the Beifongs had a child. Now they might have been training her for later when she's unleashed (er, debuted) on society but even so, she's never actually been to a function, not even a party at the Beifong estate. For a twelve year-old kid who's never been to a real soiree before, I'd say she handled herself awfully well.