Countdown To Drop Down is quite a stressful level in Super Mario Bros. Wonder, as it lets you know when a platform will fall apart, and it makes you rush when you run out of jumps. That being said, the main mechanic for reaching the Wonder Flower and triggering the event is something different.
In fact, you need to pay close attention to the behavior of your enemies, as some of them will use friendly environmental objects to annoy you, which means you can also use those objects in the same way as well. So, here is how to do it!
Wonder Seed 1
After activating the checkpoint, continue the path forward until you see a turtle flying over your head using a smiling cloud. The cloud could be yours only if you can jump over the turtle and make it fall.
The first time that the turtle appears above your head, your distance is not close enough, but as your platform moves forward, you will get higher, where you can defeat the turtle with a simple jump. Once the turtle is gone, you can land on its cloud and drive it yourself.
Keep in mind that the cloud will only remain active for a limited time, and once its energy is over, the cloud will disappear. So, be quick and move to the bottom side of the yellow pipe to interact with the Wonder Flower.
Once the event is active, you will begin to fall off. Be aware that there will be some dark clouds on your way that you need to dodge until you notice that the Wonder Seed is also falling off with you. Steer your character towards the Wonder Seed and catch it mid-air to finish the event.
Wonder Seed 2
Now that the event is over, all you need to do is finish the level to get the final Wonder Seed. If you want to reach the top of the flag bar in the end, you will either need to equip the Floating Jump badge or drive a cloud to the bar.