Related Clues:

• Concept that spreads
• Concept that spreads rapidly on the Internet
• Cultural idea that may go viral
• Viral Internet phenom
• It's hot until it's not
• The Macarena or Psy's horse dance, e.g
• Crosswords, e.g., in the 1920s
• The "Macarena" dance was one
• Short-lived thing
• Grumpy Cat, e.g
• Planking, e.g
• Pet rocks, e.g
• Viral Web phenomenon
• Current "in" thing
• Nose rings, e.g