Vs. Super Mario Bros. (Nintendo Vs. System)
Warp to World 2, 3, or 4
In World 1-2, use the elevator platforms to jump onto the ceiling above the end pipe. Behind the wall you'll find a Warp Zone, where you can skip ahead to World 2, 3, or 4.
Warp to World 5
In World 4-2, walk on the ceiling past the end pipe to find the warp to World 5.
Warp to World 6
This is the second Warp Zone you can reach from World 4-2. After the first elevator lift, there is a pit and three brick blocks above you. Jump around, and you'll find four hidden coin blocks under the three bricks. Use the hidden blocks you just uncovered to hit the first brick, which holds a Vine. The Vine leads to some bonus Coins and the warp pipe to World 6.
In Super Mario Bros., this Warp Zone lets you go to World 6, 7, or 8.
Invisible 1-Up Mushrooms
Like in Super Mario Bros., you can unlock hidden 1-Up Mushroom blocks in X-1 worlds by collecting enough coins in X-3 worlds in one life. This time around, however, not all X-1 worlds have the 1-Up blocks. Here are the remaining bonus 1-Ups and how to earn them:
Note: Vs. SMB uses the same coin requirements from the original SMB, even though Worlds 5-3 and 6-3 were redesigned and ended up with more total coins. Interestingly, World 8-1 still has the hidden 1-Up block in its map data, but since the new World 7-3 has fewer coins (24) than the requirement (35), you'll never be able to activate the bonus during normal gameplay.