Toy Time Galaxy is accessible in the Engine Room with 40 Stars.
Star 1: Heavy Metal Mecha-Bowser
Mario starts at a toy train station with two trains. One is long, while the other is short. The leader of the Toad Brigade is on the long one, while the glasses toad is on the short one. It's best to take the long one so you won't fall off too quickly. Once you take the launch star to planet #2, go right. You'll see two pipes. Walk Mario on both to find a Life Mushroom for extra health. After that, go to the pink ground to walk on the wall (you'll see the green ones at the toy robot, they use the same thing) to find a ? block. After getting Star Bits from the ? block, veer on to the pink surface on the right. Watch out for the laser robot.
Spin the screw to stop the spinning fan for Star Bits. Then you'll find a Launch Star in a cage. Spin the gold screw to free it, but don't go forward, or you'll die. Instead, veer back to the blue Gearmo (the guy with the black gear behind it) to see a yellow one in the distance. Kill the Mecha-Bowser by ground pounding its back for a coin. Go in the hole on the blue platform next to the yellow gearmo to find a blue screw. Spin it to extend a ledge over the gap under the launch star. Go across it to the launch star to get to the toy robot. At the end, get a Spring Mushroom to bounce to his head then ground pound the tall stack of stone wheels to destroy it, rescuing the Gearmo from Planet 2's friends. Get the Power Star as the friends are damaged from the explosion, but are actually okay.
Star 2: Mario Meets Mario
For the time being, ignore the Hungry Luma you meet on this level.
Star 3: Bouncing Down Cake Lane
You see the trains again but the launch star is now on the right side. When your launch star ride is over, Use the spring mushroom to wall jump up to a conveyor belt (not the one with the robot).
At the cannon, Blast off to a pull star circle with a launch star in the middle.
At the next planet, You have to blow out the candles to get a launch star.
Boss battle: Beat a cannon by using a spring mushroom.
Then you get the power star.
Star 4 (Fast Foe Comet): Fast Foes of Toy Time
This is the same as the hidden planet in Star 6 (see below), except with faster moving enemies and platforms.
Star 5 (Purple Comet): Luigi's Purple Coins
This is a difficult star to get. You land in a corner space of a very large area that forms an 8-bit Luigi. Every space of the area is a hazard, except the platform you start on. The green spaces start to disappear once you step on them, the yellow spaces begin to rotate when stepped on, and the dark green, swampy area will immediately make you lose a life when touched. There is also the ever-present danger of falling off, of course.
As usual, the goal is to collect 100 purple coins which are scattered around the area. Once you obtain 100 coins, the star will appear on the platform where you started, so try to move in a circular path. There are a total of 150 coins in the entire area so it is OK to miss a few. There is no reward for getting all 150 coins, so don't look for one. Occasionally there will be small groups of coins (about 5) in a clump off the border of the area. To get these, a very efficient way is to jump toward them, and quickly spin to move yourself to the cornered square. There will also be large gaps where coins are in a line. Long-jumping is the best way to get these coins and to get to the other side. Lastly, don't worry about the clock. You have plenty of time to complete this so stay focused mainly on not falling.
Star 6 (Hidden): The Flipswitch Chain
Enter Star 2. Proceed through the level as for Star 2. When you meet the Hungry Luma, feed it 50 Star Bits.