Stamp: 8-Bit Mario
Enter the tent from the map to claim the stamp inside.
World 12-1: Champion's Road
Yeah, this level is almost unfairly difficult, and it's long; we lost a lot of lives. Bring a Tanooki Suit if you can. That said, the first star can't be missed. It sits at the end of the beep blocks, right before you enter a clear pipe.
This one is also impossible to miss. It's right after the swinging rollers, just before you enter a warp box.
You'll find this among the huge section of dash panels a bit later into the level.
Stamp: Lucky Cat Mario
The stamp is right at the end of the level, right before you leap to the flagpole.
World 12-Special 1: Captain Toad's Fiery Finale
Drop off the ledge and let the rising lava take you to the first star.
The second star is tucked inside a block in the middle of the map. Run in and grab it while the lava level is low, then get back to the safety of a red raft.
You'll need to use blow platforms to continue forward. One of them automatically takes you to a star. Keep blowing into the GamePad mic to stay hovering above the lava.
The very next blow platform takes you to a bridge made of falling platforms. There's a star along it.
Stamp: Little Toad
When you reach the platform with the Piranha Plant, drop to the central blow platform. Use it to reach the cloud above, where you'll find this stamp and a bunch of gold coins.
Drop through the hole in the cloud to land on and defeat the Piranha Plant below. Now you can grab the final star behind it.
World 12-Special 2: Mystery House Marathon
This final stage is a series of 30 (seriously, 30) challenges, each with a time limit. For the first, you have ten seconds to defeat a trio of Koopa Troopas.
For the second, you must cross some swinging platforms. Watch out for the rolling spike on the final one.
You have to press three switches in the next challenge. Quickly stun the two Brolders that appear, then toss them onto a switch each. Stand on the third yourself to spawn as star.
In the next room, immediately hit the question mark block and grab the Fire Flower that pops out. Light the four torches for a star.
The next room is perpetually spinning. Dodge the ghosts and grab the star when it gets close enough.
The star is located in one of the crates in challenge six; you'll need to bust up the four in the upper right to find it. If you still have the Fire Flower, this will be much easier.
The next room has a Goomba and several Mini Goombas. Take them out to earn a star.
The star in room eight is down a ramp. Grab a baseball and chuck it down to collect it. If you take out a Biddybud instead, quickly throw another.
In the next room are a few of those trampoline enemies. Stun the one to the far right, and it will become a regular trampoline. Use it to reach the star.
Room ten has those walkways that only appear when you get close. Run out and ride a Thwomp to the upper level to grab the star.
Grab an Ice Skate as soon as you warp here, then move forward. The Walleyes here are absolutely annoying, but you'll have to pass them to reach the star.
Immediately hit the question mark block in here for a Super Bell. Use your Cat Suit powers to scramble over the wall, and hit the switch. Scramble back over to grab the star it spawns.
The next room is a climbing challenge. Scramble to the top as fast as you can to grab the star.
The next room has a series of beep blocks. Time your jumps up them, then scramble up the wall to grab another star.
The fifteenth room is another climbing challenge, but the blocks will descend as soon as you latch on. Scramble up quickly to reach the star.
Halfway there! In there next room are a spinning wheel and several Fuzzies. Scramble around the wheel to the star between the groups of enemies to nab it.
A tiny rabbit is inside the next room. Use the dash panels to catch it and earn another star.
You have to hit a switch on a wall in here. Grab a baseball and use the jump pad to launch yourself closer, then chuck the ball to hit the switch and spawn a star.
The next room is a giant roller. Spin the room until you can hop to a ledge, then from there, leap to the star. Watch out for the Piranha Plants too!
There are two Bullies inside the next room. Knock them into the lava for another star.
In the next room are three question mark blocks; striking them will spawn more blocks you can use as platforms. Use this to reach the star above - a ground pound is most effective on the blocks.
This next room is tough; you have to hit the dash panel to reach the star in time, but it lies across some very narrow platforms. The Cat Suit Bullet Bills won't catch you while boosted, so focus on staying on the narrow walkway to reach your prize.
This room is also very tough. You have to bounce up the sleeping Piranha Creepers' heads. A Cat Suit will make this a little easier, but not by much. Good luck!
This room has three question mark panels, all guarded by something. Chuck baseballs at the left two when the Thwomp are in the air, then turn to the bricked up column. Kick the nearby bomb into it, then chuck a baseball at the last switch to spawn the star.
This room can be tricky: it holds two Potted Piranha Plants and several Fuzzies. Pick up a Piranha Plant and use it to gobble up every other enemy. Then let it go and stomp on it to clear the room and spawn a star.
The next room is just a big roller. Dash along and avoid the Piranha Plants until the star comes into view.
The star is in the upper right corner here. Quickly wall jump between the bricks to reach it. This will activate the spotlight and send Cat Suit Bullet Bills after you, so move fast.
Start running as soon as you spawn here - you need to cross some falling platforms. These give way with the Spikes' rollers too, so you need to get to the other side and leap for the star before they fall too far.
Boom Boom appears in this room, but you only have to hit him once. Stomp on his head to earn a star.
The last room is just a walkway with coins, a stamp, and a star. Just run forward to grab it all.