New Super Mario Bros. U: Superstar Road-2 -- Run For It

If you have a P-Acorn saved up from a Nabbit challenge, now would be a valid time to use it. Here, you have to hit P-Switches to stay alive, as they make coins into brick blocks you can stand on. Just hit the P-Switch at the start and run at top speed, if you're not going to use the P-Acorn. There are several pipes with Piranha Plants overhead, but the Piranhas won't bother you if you're running at top speed. Keep running and jumping and be sure to hit the next P-Switch overhead. After hitting the third P-Switch, you'll have to platform on brick blocks. The first Star Coin is surrounded by brick blocks, so as Super Mario, pound the top layer of brick blocks only to get the Star Coin. You should have just enough time to reach the Piranha Plant in the pipe. When the switch runs out, there will be several coins next to it. Drop down to collect the coins and land on the next P-Switch. From here, you'll see a lot of Koopas. Use the shell of the first one to clear them all out, running after the shell as you go. Don't worry if you get close to the shell. If you clear all of them, you'll get three 1-ups. The next P-Switch is near the last Koopa. Next is a set of platforms with lots of Koopa Paratroopas flying around, one near the second Star Coin. Wait for it to get close to the Star Coin, then bounce off it to get the Star Coin. Quickly run to the right and time your jump so you bounce off the next Koopa Paratroopa to hit the P-Switch above it. This can be tricky. Drop down to moving brick blocks. You'll have to time your jumps because they move quickly. They will take you to the next P-Switch, which is under a ledge. Wall jump to hit it. Keep going, and you'll see the third Star Coin right next to the flagpole. Either triple jump up the brick blocks or fly and boost to get it.