I never forget a face, but in your case, I'll be glad to make an exception.

The joke turns a polite-sounding compliment (“I never forget a face”) into a cutting insult by adding an “exception” for the listener. The humor depends on reversal and timing: the first clause raises expectations of admiration or good memory, while the second reveals contempt—implying the person’s face is so unpleasant the speaker would prefer to forget it. Beyond the insult, the line showcases Groucho’s comic persona, which treats social niceties as setups to be punctured. It also exemplifies a classic strategy of one-liner comedy: weaponizing conventional phrases by twisting them into unexpected, antagonistic endings.

1) "I never forget a face, but in your case I'll be glad to make an exception."
2) "I've never forgotten a face, but in your case I'll be glad to make an exception."
3) "I never forget a face—but in your case, I'll make an exception."