This unusual scene is from a special 2005 Valentine's Day episode of WHAT'S NEW SCOOBY DOO? Here Fred confronts a red-eyed and rabid-looking Scooby Doo (more like Scooby-Doom, amirite?) who will later turn out to be merely a bad guy wearing a Scooby-Doo mask.
This very special Valentine's Day episode featured pop musician JC Chasez, who is not pictured here. The episode, strangely, also did not feature Fred pitching woo with either Daphne or Velma.