From the Super Mario Wiki
The Spear Thicket is a location in Mario Party Advance that is found in the Jungle Area of Shroom City. It is a leafy area dense with green, thick bushes, and it is also the roaming area of Spear Guy, a duelist who is only interested in challenging people with mustaches. Visiting the thicket as either Princess Peach or Yoshi causes Spear Guy to simply dismiss them, while visiting the thicket as either Mario or Luigi compels Spear Guy to challenge them to a duel. Accepting starts the Mustached Hero! quest, and winning earns the player the Tank-Down minigame that they play during the duel.
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