Potentially working as an extra on Indiana Jones 4 later this month has me thinking about my two previous experiences in that capacity.
The first was Fever Pitch, the 2005 film starring Jimmy Fallon and Drew Barrymore. Several scenes were shot in Fenway Park, a small section of which Boston Casting filled with paid extras. Not the whole stadium, though; in any sufficiently wide-angled shot, if you look far enough back, you'll notice none of the fans are moving. That's because they don't have legs. To save money on actual extras, inflatable dummies often fill in the seats that no one will notice beyond whether or not they're occupied.
It took a long time to set up each shot, what with lighting, makeup, cameras, and conferrals among the production crew. Every scene had to be filmed multiple times from multiple angles, so the extras huddled under their jackets, waiting for the call to "Action!" before shedding their covers and acting warm until "Cut!" signified it was safe to warm up again while the crew reviewed the recent footage and prepared for more. No noise was permitted; we mimed our actions, with cheers or catcalls (which may otherwise drown out the main characters' dialogue) dubbed in later. I didn't see Drew Barrymore, but Jimmy Fallon seemed happy to be surrounded by fans. We kept him company that September night from 6 PM to 6 AM — probably the first all-nighter I've ever pulled. (Driving home, I noticed my framerate had dropped considerably.) But it was all worth it:

Click for larger image.
The other movie I've worked on was The Game Plan, starring Dwayne "The Rock" Johnson. I worked as a sideline photographer at Gillette Stadium in Foxboro and again at Fitton Field at Holy Cross in Worcester. Each required showing up at 4 AM, which meant rolling out of bed at 2 AM. It was wet and dreary that October, and though I was spared the false enthusiasm of pretending to be a fan in the bleachers, I wasn't able to remain seated like they were, which was exhausting. Hundreds of extras reneged, to the point that Boston Casting desperately offered iPod raffles as an incentive for people to show up. I don't know if I'll be visible when the film hits theaters in September, but, as with Fever Pitch (which I've never actually watched, except for my scenes), the DVD will likely prove more enlightening.
Long hours, crappy food, and minimum wage — I'd decided additional extra work would give me insufficient compensation to warrant pursuing further opportunities; they'd just be redundant on my resume, anyway. But, unlike Sean Connery, for Indiana Jones, I'll come out of retirement.
A friend wanted to see me in Fever Pitch for herself. So here are the time indices to look for me:
1:29:22
1:30:21 to 1:30:32
1:30:58 to 1:31:31
The Game Plan comes out on DVD in widescreen, fullscreen, and Blu-Ray on January 22nd.