The inside jokes in Lucky Star always bring a smile to my face! In this epiosde (number 12) the otaku ladies go to Comiket, which is the world's largest comic book convention:
"The first CM was held in December 1975, with only about 30 participating circles and an estimated 700 attendees. Attendance has since swelled to over a quarter of a million people. The convention lasts for three days. It is a grassroots, DIY effort for selling dōjinshi, self-published Japanese works. As items sold in CM are considered very rare (because dōjinshi are seldom reprinted), some items sold at CM can be found in shops or on the Internet at prices up to 10 times the item's original price."