It looks like Chipotle is doing their free burrito promotion again this Halloween, from 6 to 10 pm. Dress as a burrito (or something less complicated, but apparently it needs to include foil and be somewhat in the vein of the burrito concept - maybe a crown?) for a free burrito.
I'm not going to attach a link because I keep getting some suspicious activity when I try to click on anything that includes the words "chipotle halloween promotion october 2009." In the interest of saving both our computers from a mess to be cleaned, I'll just tell you to check with your local Chipotle.
Update 10/31/2009: It worked! I went to Chipotle with a aluminum foil crown on my head, and I got a free salad! The guy behind the counter teased me that I was a burrito princess. There were lots of people there who were not wearing any sort of costume, and my sister refused, but I saw at least one whole family wrapped in various aluminum foil accessories. Cool, huh?