Send Out the Clowns is a challenge in Southwind Express. It is unlocked by killing all five Hobos on the train.
The Final Hobo can be hard to find. Once you have completed the final battle, do not exit. Climb up to the top along with some explosives, such as the cherry bombs obtained just before. Go left, and blow up the blocks to reach the last hobo.
Community content is available under CC-BY-SA unless otherwise noted.