I was asked to give an answer, and I'm providing two: one that directly addresses the request for a "pick up line", and one that may address the larger issue of expressing interest in, and building attraction with, someone with Asperger's Syndrome.
Pick up line: "I dunno anything about Asperger's, but those buns sure look well done to me."
General tactic: you can think of Asperger's Syndrome as just sitting near a behavioral/cognitive extreme, or perhaps more accurately at several extremes for various aspects of personality. The normal rules apply, it's just that some of the rules apply "double".
In relating with and connecting to people with Asperger's Syndrome, the number one element that works is this: a very deep understanding of Asperger's Syndrome, to the point where you can start differentiating between what is pathologic, and what is simply a personal quirk of your love interest.
As for how best to approach and attract specifically, the consensus seems to be a combination of the following:
- flexibility (of mind and opinion – though I'm also convinced that being able to visually inspect one's own butt has a pretty universal appeal)
- clarity/simplicity (of focus, communication, you name it)
- patience, again!
You may start to notice a theme or pattern above, namely that pursuing a relationship with an Aspie requires a lot of patience, and I might even say a sort of "detachment" – to outcomes, expectations, and anxiety.
If being in a relationship is part of what makes you whole, then you won't be able to tolerate some of the treatment you are likely to receive over time… And indeed your object of interest may find YOU to be less interesting, as well.
Tactically, I'd recommend simply focusing on your mutual interests and aptitudes, and crafting several "no strings invitations" to events/activities she's likely to enjoy on her own.
Never try to pawn something off as "merely friendly", in the hopes of becoming more later – what is normally just pathetic may come off as genuinely dishonest, or even confused. Similarly, the example pickup line written above is actually a terrible one to use with an Aspie. Unless, of course, they are also obsessed with wordplay (in which case they'll probably simply miss that you're hitting on them)
Instead, make it clear that you are interested, but that you're also happy to share these adventures regardless of outcomes. And, most importantly, make sure that it's actually true.