Luton Town officials were baffled by Arsenal's celebrations after their win at Kenilworth Road last week.
The Gunners fought back from 2-3 down to win 4-3 at their London rivals in the final minutes.
Arsenal players and staff celebrated raucously in the away dressing room, much to the bemusement of Luton officials.
A source told the Daily Mail: "You'd have thought they'd won the league, not nicked a win at little Luton."
The win saw Arsenal return to the Premier League summit before they tumbled again after defeat at Aston Villa.