Fiona’s scorned hubby Gus wanted to be heard on Sunday’s Shameless, and he certainly was — loud and clear! — when he performed a scathing tune in front of his estranged wife and a club full of onlookers.

Titled “The F Word” — the “F” is for “Fiona,” among other, not-so-nice things — the ditty “was so much fun” to sing, actor/musician Steve Kazee tells TVLine.

“It’s a horrible song, and it really makes Fiona feel awful,” but the earworm was so catchy and well-written that “a lot of people were still singing it [on set] throughout the day,” he adds.

Now you can listen to “The F Word” and have it get stuck in your head, too, by pressing PLAY above.