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Useless motherfucker -- that's what she called me! "It's either ME or Iggy Pop, time to decide!".
— Tommy ‧ Trainspotting

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The speaker bitterly repeats an insult, being called useless, and mimics a partner's ultimatum to choose between them and Iggy Pop. The crude phrasing and quoted demand make the grievance sound wounded yet comic, as though the speaker is still stunned by the choice.
Context reviewed