I'm not seeing any game I like above.
WIA is partially right that this
could be her pickup line. But, remember one more thing: Even if that's true, in this dynamic, you're no longer receiving a single sloppy line from a semi-interested girl. This is a more complicated setting.
First of all, there's something none of you are considering.
Girl 2 might have straight-up trying to cockblock (subtly), under the guise of "rescuing" Girl 1 (which I'd say is a 50% chance, depending on the setting, which you didn't describe in enough detail). Outgoing girls will try to Tina Fey you with these wannabe clever lines and some delusional belief that they're in on the joke with the other girl and
you're just the stupid man from the Super Bowl commercials they just saw.
But, even if this
was a weak-handed attempt at landing a line on you, you're no longer responding as if you're talking to one girl--which is all I'm seeing in the responses above.
You're now playing to an audience, and you have to respond accordingly. You need to say something that's funny enough that one, or both, chuckle. There's a subtle, but supremely important, difference between the two. You have to open the field to the possibility that another challenger has entered the ring.
She might be interested in snatching you from this other girl.
So your line has to do a lot of things at once. It has to be playful, but also ever-so-slightly ridiculing.
It has to be self-effacing, but not too much, and definitely not cocky-arrogant (that "in your dreams" noise) as if you were talking to one girl, outside of a nightclub instead of this way-more-complicated situation.
If
I'd heard that line--even if I was 10,000% sure I'd never see that bitch in my life--I would have immediately changed gears.
Girl: "You look familiar."
I would have
gotten a little theatrical, nodding yes very slowly, while squinting as if I was trying to place her, and maybe putting my hand on my head. I would have then stalled for a few seconds, and delivered my line as if I'd had an epiphany. No corny tone or body language. Sounding as it was 100% real.
Tuthmosis: "That's right. [snapping fingers and pausing for effect] You were in my gamblers anonymous. How's your issue? Are you clean now?"
This will get some kind of laugh and
gives her (and them) an opening to play along and be silly. Then you can game as if you're talking to
two girls, because you are. See which one wins your attention. If she was trying to cockblock, she's now neutralized because Girl 1 sees you're cool. If Girl 2 wanted the D, she now wants it more.
This is a win-win-win.