World 4-5 introduces the Spikes, an enemy that stands still throwing spiked rollers that need to be avoided. At the start, head up the steps and deal with the Spikes and Galoombas, as you come across them. Use the ?-Block to find a power-up (Super Bell, if big), then head up the ramp while avoiding the spiked rollers. Once you reach the top of the incline, go on top of the nearby wall and follow it to the end to find the Stamp. Return to the ramp and you should see a pipe across from the top of the wall.
Enter the pipe to find a bonus area, with some switch panels and some more Spikes. Your objective is to turn all of the switch panels, but the Spikes will continually toss spiked rollers on them (they don’t switch the panels with them). Since there’s no time limit here, you can easily just go defeat the four Spikes, then turn all of the switch panels to spawn Green Star #1. Exit the bonus area and continue through the main course, with the next obstacle being some swinging platforms that have spiked rollers on them. In the middle of them will be a break, and the Checkpoint Flag.
On the other side, you will find some Galoombas waiting for you, as well as another large ramp that has Spikes doing their thing. Before heading up the long ramp, ground pound the circle of flowers to reveal a Super Star. Rush up the ramp and through the Red Ring, then collect all eight Red Coins for a Super Bell. You will need this Super Bell, too, as at the top of the ramp, there is a large wall you must climb. Once you manage to climb to the top with the Cat Suit, run to the end of it to find Green Star #2.
Drop back down to the main course and past the three Spikes at the top of the ramp, you will come to more swinging platforms. Ride them, while avoiding the spiked rollers, and after the second spiked one, there will be one off to the left that has Green Star #3. From there, continue to the end, where there is one final ramp and the Goal Pole.