I saw this in Wired, and it struck me so funny, about a trademark flap between rival 'fart gadgets' and in case you needed clarification on the phrase 'pull my finger' here it is, courtesy of Kevin Houchin, InfoMedia's lawyer:
The phrase "pull my finger," and derivations thereof, are generally known and widely understood in American society to be a joke or prank regarding flatulence. The prank begins when the prankster senses the deep stirrings of flatulence. The prankster then requests that an unsuspecting person pull [his or her] finger. The prankster extends his index finger to the victim. As the victim pulls the prankster's finger, his flatulence erupts so as to suggest a causal relationship between the pulling of the finger and the subsequent expulsion of gas. In other words, the phrase "pull my finger" is understood to be a description of the act of passing gas.