Stamp: Happy Sprixie
Enter the bonus tent on the map to find a stamp inside.
World 2-1: Conkdor Canyon
Use a Cat Suit to scramble up the first tall platform you see. Up here, you'll find a few coins and a star.
Just after passing the narrow walkways with several Conkdors, you'll come to a single Conkdor in the center of some big bricks. Stand near them to have him break them with his beak - one of them holds a star.
As you near the end of the level, continue just past the many moving platforms. There's a Conkdor here attacking a Toad. Defeat the Conkdor, and the Toad will give you a star.
Stamp: Jumping Mario
You can’t miss this one. It's right before the many moving platforms at the level's end.
World 2-2: Puffrod Peaks
Early in the level, you'll see two touch platforms under some bricks. Touch the right one - notice the hole underneath? Drop in to find a hidden chamber where you can touch another platform to reach a stamp.
When you reach the wall of touch platforms, keep left. Wall jump into the nook to reach the star up here.
Before hopping off the trio of blow platforms, hop to the left one and ride to the cloud. This will launch you to a secret area. Dash through this course to find a star at its end.
Just beyond is a trio of touch platforms. Activate the first two, then blow into the GamePad mic to attract a hidden blow platform. Ride it to another star.
World 2-3: Shadow-Play Alley
You'll see the shadow of the first star shortly into the level. Simply walk into the foreground to grab it.
Stamp: Piranha Plant
You need a Cat Suit for this. After passing the giant Piranha Plant, drop into the pit to the right. The bricks to your left can be clawed through to reach the stamp.
In the next section, you'll see this group of pink eye blocks. Touch them on the GamePad, and they will briefly disappear. Do this and quickly jump through the wall to reach a mystery block. Inside the secret area, you'll have ten seconds to hit the blue switch and grab the star it reveals.
Before going through the last red door, walk through the gap in the bricks to your right. In here is a Toad being tormented by Bowser…or is he? Walk into the foreground to find a moving cardboard cutout of Bowser. Walk into it to tip it over, calming the Toad and earning you another star.
World 2-4: Really Rolling Hills
Stamp: Little Mario
From the start of the level, head right to find a Mario switch. Use Mario to hit it and reveal stamp.
You'll need a Cat Suit for this. Ride the first clear pipe, then scramble up the wall to find this star on a higher ledge.
When you enter the underground area, look for this warp pipe along the path. Take it to a secret area, then get moving. Every tile in here needs to be stepped on before the music stops. Do this, and you'll receive a star.
When you reach the three wooden wheels, drop between them. There's a secret area down here with a star.
World 2-A: Big Galoomba Blockade
Simply take out the Galoombas to earn a star.
World 2-5: Double Cherry Pass
Destroy the crates near the clear pipe to reveal a star.
As you leave the tunnel, be sure to hit both tiles to reveal another star.
Stamp: Fire Flower Peach
You need a Cat Suit for this. When you reach the multicolored hills, move to the back left corner. Use a Double Cherry clone to hit the leftmost question mark brick and reveal a brick above. Keep hitting the question mark to create a whole column of bricks. Use a clone to quickly scramble up this column to reach a stamp.
If you have at least four Double Cherry clones left by the level's end, hop onto the elevator tile. It will rise up to another star.
World 2-Special: Mystery House Melee
In the first room, you'll have 10 seconds to take out the Galoombas. Do so to earn a star.
Do the same for the Koopa Troopas in the second room.
Do it again for the Cat Suit Goombas in the third room.
…and again for the Conkdors in the fourth room.
…and one last time for the Fire Bros. in the final room.
World 2-Castle: Bowser's Bullet Bill Brigade
The level's first star is by a group of Piranha Plants after the first caravan.
The next star is inside the first box on the second caravan.
Stamp: Boom Boom
This will float by during the second caravan. Quickly break the boxes to reach the platform where it rests.
Hopefully you managed to keep the Bomb Box on your head through the whole level. Just before hopping into the warp pipe, fire a shot at the wooden Bowser wall to reveal star behind it.