Bowser Jr. Space
From the Super Mario Wiki
Bowser Jr. Spaces are a variant of minigame spaces in Mario Party 9. When landed on, Bowser Jr. will appear and challenge the captain, as well as a randomly chosen second player, to a Bowser Jr. minigame. However, if a CPU captain lands on this space, Bowser Jr. will always force a human player to play his minigame with the CPU captain.
If the team wins, they get five Mini Stars each; if Bowser Jr. wins, he will take five Mini Stars from both players.
If only two players are playing, however, this space will not be present. Likewise, there are no Bowser Jr. Spaces in the DK's Jungle Ruins board.