Headscratchers / Scooby-Doo! and the Loch Ness Monster

• During the bit where Shaggy and Scooby encounter the monster in the forest, the bit where Scooby drives the Mystery Machine, who spun the sign that led them to encounter the monster? We just see a gloved hand and it isn't really remarked upon further.
  • Maybe Colin or Angus? They are pranksters.