The unseen meme is deadliest.

A meme is "an idea, behavior, or style that spreads from person to person within a culture". A meme acts as a unit for carrying cultural ideas, symbols, or practices that can be transmitted from one mind to another through writing, speech, gestures, rituals, or other imitable phenomena with a mimicked theme. Supporters of the concept regard memes as culutural analogues to genes in that they self-replicate, mutate, and respond to selective pressures.

Nice meme![niceme.me]
FrankerZ[tehurn.com]
The biggest meme of them all![forums.timetokill.net]