World 3-7 will introduce the Switchboard to the game, which is a platform that has two arrows on it. By standing on either of the arrows, the switchboard will move in that direction (they are almost always on rails). You can also use the touchscreen or cursor to hit the arrow on either side, for those not playing it with a normal controller. Hop aboard the first Switchboard and ride it over to the next island. Hit the ?-Block to snag a power-up, then climb up to the left for a hidden ?-Block that has a 1-Up Mushroom.
This level will also introduce the Fizzlit, a small purple blob that has a nasty surprise for you if you try to jump on its head. After a few seconds, the Fizzlit will “melt” and turn into an electric puddle, so you will need to time any contact with your character when it’s not doing this. Head over to the right now, defeating the Fizzlit and riding the switchboard to a switch block, which will change the track so the switchboard can get across to the other side. There are some bricks here, but what you don’t see are invisible ?-Blocks, with the top one containing a Super Star.
Use this Star to take out the enemies ahead, then hop onto the switchboard to reach the switch block. This will change the track so you can go down the mountainside, but you will want to be alert, as you need to jump off and into an alcove that has a green pipe. Inside, you’ll want to just fall and follow all the coins to easily reach Green Star #1. You’re brought back at the Checkpoint Flag that positions you at a bunch of Switchboards. Make your way across carefully, grabbing the Red Ring and its related coins for a Fire Flower. Clear out the Stingbies as you enter the cave behind the waterfall, then drop down to a switchboard.
As soon as you land on the switchboard, go to the left arrow and duck, where you will go underneath and behind the waterfall; Green Star #2 will be behind the waterfall here. Make your way back to the right, where you’ll need to time your hits on the Switch Block to thwart the Fuzzlers that are rolling around. The switchboard you’re on will fall when you hit the final switch block here, so just ride it right and jump over the Fuzzler as you go uphill to Green Star #3. Make your way back left, dropping to the final switchboard below you when you see it. Ride this one right and you should find the Stamp in the air, so grab it, then continue to the Goal Pole.