You can collect several 1-Up Mushrooms on Spaceship Mario. As you collect stars, the following 1-Up options will appear on Spaceship Mario.
Grab Yoshi off of the "nose" and use the star pegs to swing up to a hidden island with 10 fruit. Eat them all for a 1-Up.
Grab a Cloud Flower and make platforms to reach a 1-Up on a cloud high above.
Spin into the random item block for a chance at a 1-Up.
Near Mario's left ear (your right) is a warp pipe that takes you to a 1-Up minigame. Feed the Luma to spin a number of random item blocks for a chance to win 1-Ups.
Talk to the Gearmo Robots when they show up on the planet to receive 1-Ups.
All Luigi ghosts
Collect 9,999 to unlock all the Luigi ghosts without having to complete each level as Luigi.
Alternate Ending
Collect 120 Stars to see an alternate ending cutscene with Rosalina reading to Lumas and discussing Green Stars.
Bank rewards
Deposit the indicated amount of Star Bits with the Bank Toad to unlock the corresponding item.
Glasses: 1,000 Star Bits.
Spear and shield: 2,000 Star Bits
Pickaxe: 4,000 Star Bits.
Diver Toad: 6,000 Star Bits.
Explorer Toad: 9,000 Star Bits.
The Perfect Run (Grandmaster Galaxy Daredevil Run): 9,999 Star Bits.
Cloud Mario Cataclysm
In the Shiverburn Galaxy, get really close to a Cloud Flower and let yourself get singed by a fiery projectile. Quickly grab the Cloud Flower. You should see that the three clouds follow Mario but we will not be in his Cloud Form.
Co-Op mode sound effects
Press Up, Down, Left, or Right on controller two to make sound effects on player one's Wiimote. Press Minus, Plus, 1, and 2 on controller one to make sound effects on player two's Wiimote.
Creepy Mario
If you make Mario look at the camera, and go into the first-person viewing perspective, the camera won't turn around to reorient. Check out Mario's face.
Death counter
Collect the final star in The Grandmaster Galaxy (The Perfect Run) to see the number of deaths you have accumulated on your saved game file.
Defeating the Boomerang Bros.
Press Z to crouch to avoid their boomerangs. Walk over to the Boomerang Bros. while crouched, then spin to kill them.
Die during the credits
Collect a Bee Mushroom during the credits and wait for the Shiverburn area to start. When the page flips, fly toward the screen before you appear. If done correctly, you should die by falling. The screen will turn black while the sound effects from the credits play. At the end, it will read "THE END" with "TOO BAD" in the background.
Duck the Boomerangs
When you're facing the Boomerang Bros. you can crouch (press Z on the nunchuk) to avoid the boomerangs. Walk over to the Bros. while crouching and spin to kill them.
Easy lives
Use the following trick to get 99 lives with two players. In World 4, enter the Supermassive Galaxy. You will eventually reach three turtles walking around in a circle. Take the Spin Drill and kill all but one of the turtles. Have the player two hold the last remaining turtle. Have player one run and jump on the turtle's back from behind it. Stay on the turtle. You do not have to do anything (such as pressing A as soon as you get on its back); Mario will jump anyway. Use the Wiimote to stay on its back so you do not jump off. You will get 99 lives from this, but they will not be saved after you turn off the game. This trick must be repeated to get the lives back.
Flipping high dive
Get to a location that is high above deep water, for example at Starshine Beach Galaxy. Run up the small sandy incline at the beginning. Search for a wooden plank hanging off a side. Have Mario move to the edge and he will look down at the water. Turn around while standing there, then hold Nunchuk Z and press Jump to perform a flipping back flip dive.
Gold Crown at profile select
Get all 242 stars.
Grandmaster Galaxy
Collect 120 gold stars and 120 green stars to unlock the Grandmaster Galaxy in World S. This is a 2D level with a Comet Medal and a one star to collect.
Green stars
Successfully complete the game with 120 gold stars to be able to collect 120 green stars.
Infinite (Very Slow) 1-Ups on Starship Mario
Collect some 1-Ups on the ship with either Mario or Luigi. Switch to the opposite character, and the 1-Ups will be back! Switch back, and they will still be there.
Infinite Lives
This fantastic cheat will get you 99 lives easily -- you can always return for more! Go to the Supermassive Galaxy in World 4 and choose the first Star challenge. Play through the level until you get to the hockey puck-shaped planet with three supermassive Koopa turtles patrolling it. DO NOT grab the Spin Drill -- you'll have to get hit to lose it if you do! Run up behind a Koopa and long-jump (press Z while running and then press JUMP) onto its back. You need to long-jump from about a turtle-shell-length behind it to catch the "sweet spot." Continue to hold the analog stick to the RIGHT and hold JUMP to continually bounce off the Koopa's shell. If you fall off or hit the head, try again. If you hold these buttons you should be able to maintain momentum while constantly bouncing on the shell. After a few bounces you'll rack up 1-Ups for each hit.
Infinite Starbits
Go to Chompworks galaxy and pick the first Star. Go to the second planet. You know that Chomp that runs into the robot? He produces starbits! If he stops, just enter and exit the pipe.
Longer jumps
Get a running start then do a triple jump. As soon as you land, do a long jump to get twice as far. Note: This will be easier to do if there are no gaps to avoid.
Luigi gives out Star Bits
If you see Luigi at the beginning of a galaxy, have player two point him and press A. Then, have player two spin to make Luigi give out Star Bits.
Luigi on Title Screen
Exit the game while playing as Luigi instead of Mario and you'll see his face on the title screen (as long as you chose Mario's for your default profile face).
Play as Luigi
Collect The Flotacious Blimp Fruit star in the Tall Trunk Galaxy. You can now talk to Luigi at the beginning of certain levels to control him.
To play as Luigi in any level, defeat Bowser at Bowser's Galaxy Generator. Then, check the Mail Toad. You should receive a message from him. Enter the "L" on the spaceship to switch to Luigi.
Rosalina Icon
After completeing the game by with all 242 Stars, Rosalina will appear as a game icon on the title menu.
Save Your 1-Ups
You usually start the game with 5 lives, even if you save the game. You can use the "Mysterious Letter" to save all of your 1-Ups between gaming sessions -- it's slower than just racking up a bunch of lives using the turtle method each time you begin a game, but here it is anyway: If you start a different save file (you can simply copy your file over), it will automatically pass on all of the lives you had in the other file through Mailtoad. Save and quit, then return to the file you want to play and the lives are passed back again. Note: If you go into the same save file twice in a row you'll get the 5-Up Princess Peach letter instead.
Saved game profile icons
Collect 120 stars to mark that saved game profile with a silver crown.
Collect 240 stars to mark that saved game profile with a gold crown.
Collect 242 stars and become the "Master of Galaxies" to mark that saved game profile with a platinum and jewel crown.
Collect all 120 Power Stars and defeat Bowser again to mark that saved game profile with a Rosalina icon.
Secret World
Beat the game once.
Silver Crown at profile select
Collect 120 stars and defeat Bowser.
Skate backwards
Press Z while on ice.
Spin Kick
Crouch by holding down the Z button on the nunchuk and shake the Wii Remote to spin to do a Spin Kick. You can crouch to avoid Boomerang Bros. and crouch-walk up to them to kick them. Jump again to perform a second spin immediately with little pause between the two.
Super Ground Pound
Jump, shake the Wimote to spin, then quickly press Z.
Super Mario Sunshine reference
The Twisty Trials Galaxy resembles the secret level of Ricco Harbor in Super Mario Sunshine.
Super Punt
When you are close to a Hammer Bro., do a long jump and spin. Mario will kick him down, then finish him of with another kick.
Super Secret Dive
Mario's move list is seemingly endless -- even expert players may not be aware of this one. To perform the awesome flipping high dive, you need to find a place high above deep water. Try Starshine Beach -- run up the small sandy incline at the start of the level and look for a wooden plank hanging off of one side. Walk to the edge and Mario should look down at the water. Turn around while standing in this spot and perform a back flip by holding Z on the nunchuk and pressing JUMP. Mario will then perform this obscure move.
While on the wooden plank in Starshine Beach Galaxy or on the ledge with the 1-Up mushroom in the Slimy Spring Galaxy, run until you are at the edge, stop and then jump in one, FLUID motion. Mario will perform a front flip and then dive.
Time trial developer ghosts
Successfully complete a level as Luigi. A "ghost" of developers completing that level will become unlocked, for you to beat.
Watermelons instead of coconuts
Collect 9,999 Star Bits.
World S
Successfully complete World 6. World S will be available after the ending sequence.
Yoshi Infinite Flutters
Jump holding A and before you finish Fluttering (while still holding A) press Z, then quickly release A, then Press A again. Rinse and repeat.
