Behind Enemy Lines
From SmashWiki, the Super Smash Bros. wiki
Behind Enemy Lines (known as Homeward Struggle in PAL versions of the game) is a single-player event match in Super Smash Bros. for Wii U. In the event, the player, as Fox, must survive against Mega Man and Bowser Jr. for 1 minute. The stage is set on Orbital Gate Assault starting on the first missile. All participants start every stock at 200% damage. Clearing this event will award the Tricky trophy.
This event is unlocked by clearing Pokémon Battle. Completing the event awards the Tricky trophy on the challenge board, but does not unlock any additional paths. Once both the event is completed and Mr. Game & Watch is unlocked, the left path is unlocked.
Completing the event on normal or hard difficulty while KO'ing at least 8 opponents awards a Desperate Speedster Jacket equipment.