When Bart and Lisa are helping Bette Midler pick up trash on the highway, Bette picks up an empty can which says Buzz Cola on it. Just as she yells, "You pigs!" the label on the can switches to Duff Beer.
The opening and end credits title cards for the "Worker & Parasite" cartoon are written in presumably Russian or a similar Cyrillic-based eastern European language, however the words are just random strings of Cyrillic letters (and some non-Cyrillic letters as well as letters that don't exist) and are total gibberish.
According to this episode, Bart hates Gabbo, but in the comic, "Dullards to Donuts," from Simpsons Comics 38 and Simpsons Comics Unchained, Bart holds a protest sign (that makes zero sense at all, as the protest is against addictive donuts) that states that he likes Gabbo.