lemming effect 

To get in an unnecessary line because you think you are supposed to. Most often at the entrances to concerts or other events, when there are several lines and it is difficult to discern which one is needed.

Person: "I stood in line for tickets for an hour, only to find out that I was in the line for people that already had tickets. I had to get in the ticket line, then go to the back of the line I was just in. The lemming effect strikes again."

lemming effect by xodusprime August 12, 2008

Lemmings Effect 

The effect noticed when sleep-deprived friends spend enough time together that nearly everything becomes funny. Mundane, everyday, happenings become ridiculously hilarious, and normally funny jokes become so hysterically laugh-out-loud funny, you'll be in danger of dying from asphyxiation. Named because the SNES game "Lemmings" quickens the onset of the Lemmings Effect.

"What're those two laughing so hard about?"
"I think one of them dropped her pen. That's the Lemmings Effect for you."

Lemmings Effect by Kishmo November 24, 2004