Team Fortress 2 launched in 2007 as Valve's class based team shooter, with the fast talking Scout voiced by Nathan Vetterlein. The Spy is the enemy class built around disguises, invisibility and instant backstab kills, so an enemy spotted callout is always urgent for the team. Lines about catching the Spy became shorthand in the community for that paranoia, and short voice clips spread through forums, YouTube edits and soundboards. The quote stays popular because any game with a hidden traitor or impostor makes the same joke instantly understandable.