"Shooting my scene with funny, beautiful Kristen Wiig," said Aykroyd. "Lady Ghostbusters are adorable, hilarious and badass! Exhilarating!" It'd be lovely to think he showed up as Ray Stantz, but some rumourmongers believe he's just playing a cab driver: his presence a simple wink to the audience. Aykroyd has since deleted the tweet, but the ghost was already out of the trap.

http://www.empireonline.com/news/story.asp?NID=44870