With filming on the new all-female "Ghostbusters" reboot well underway in Boston, it's going to be hard to keep any cameo appearances a secret. Especially when that cameo is by one of the original Ghostbusters — and co-writer of the first two films — and when he confirms his participation via Twitter. But then, that's modern Hollywood for you. "On GB set shooting my scene with funny, [beautiful] Kristen Wiig," Dan Aykroyd posted to Twitter, though he soon deleted it. "Lady GBs are adorable, hilarious and badass. Exhilarating!"

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And if that's not good enough for you, film blog Indie Revolver actually has the details of his cameo, thanks to an on-set source with very good hearing. There should probably be some kind of spoiler warning here, but: The scene involves Wiig trying to hail a cab driven by Aykroyd, who gets to shout the iconic line, "I ain't afraid of no ghosts" before he drives off, leaving Wiig to respond, "That's a double negative! That means you are afraid of ghosts!"

Sounds delightful.

Follow Ned Ehrbar on Twitter: @nedrick