Level 2 In the area prior to the battle with Le Rauxe is a tall outpost. Climb up to the top and notice the small white cloud directly to your left. Jump onto the cloud. It will support your weight. You will also notice some more white clouds in sequence. Jump from cloud to cloud, get the Catnip power-up, then proceed to the platform towards the secret area.
Level 13 This area is tough to reach. Once at the end of the level, enter the Boss fight with Redtail. He will start to fire his pistol at you. Dash over and dodge until you reach the end of the small sandbar. Get a running start and jump as far as you can into the water. If you are lucky you will land on a small platform hidden in the water. The platform will take you to a skull and an extra life. Get them both and return to the battle with Redtail.
Level 14 Prior to the long corridor that leads to Omar, there is an invisible platform just before the overhang starts. Get a running start and jump onto it. The platform is positioned against the wall. The platform will take you up into the final secret area.