Super Mario Advance Secrets (GBA)

Super Mario Bros. 2 received another enhanced remake as Super Mario Advance, the first Super Mario title for the Game Boy Advance, which also contained a remake of Mario Bros. It included several graphic and sound enhancements in the form of enlarged sprites, multiple hit combos, and digital voice acting. Two notable additions are the new character, Robirdo, a robotic Birdo who acts as the boss of the third world, and the Yoshi Challenge, which encourages players to revisit stages and search for Yoshi eggs.

Nintendo's decision to choose it as the Game Boy Advance launch game was seen by some as misguided. Nonetheless, it was a best-selling launch game, showing that the game still appealed to Nintendo fans. Recently, the game has become part of the Player's Choice lineup for Game Boy Advance as one of the system's first 3 Player's Choice games (along with Mario & Luigi: Superstar Saga and Super Mario Advance 3). (Wikipedia)

Secrets

99 Lives
Go to World 3-3. Climb the ladder then jump over the spark enemies to the door over on the ledge. Find the red grass patches; the last one is a shell. Pick it up. Go back to the bottom of the area, and then toss the shell into the doorway. Stand on the ledge and wait. After the shell defeats enough Shy Guys to earn 1,600 points, you'll start earning extra lives. You can easily, and quickly, earn up to 99 lives.

Bald Birdo
When you get to the green Birdos jump on her head and press B to pick her bow up. Birdo will be bald!!! If you throw the bow back at Birdo it will land back on her head.

Decorative Mario Heads
For every 2 million points you get in Super Mario 2 game, you get a little Mario head next to the High Score! The maximum is 10,000,000 points / 5 heads. Any more points will NOT get more heads.

Free Hearts
If you're ever in need of hearts, look for one of those giant Shy-Guy enemies. Jump on it, pick it up, then throw it on the ground again. A heart will come out for you to collect. You can do this an infinite number of times to the same giant Shy-Guy, too.

Gain an extra life in each level
To gain an extra life in any level, collect all 5 Red Coins scattered throughout each level.

Warp to World 4-1
In world 1-3 after you get the magic bottle/potion go all the way to the right until you reach the vase thing. Use the magic bottle/potion, jump on the vase and go down. Instead of not being able to go down you'll now be warped to world 4-1.

Warp to World 5
Go to level 3-1. Go to the waterfall and go down. Keep going until you reach the hill, go in the door on the hill. Pull up veggies until you get a potion. Go to the right and place the potion next to the pot. Enter subspace and go into the pot. You will be warped to the 5th world.

Warp To World 6
In the beginning of level 4-2 jump down onto the whale and go to the left. You will find some red grass patches which will have a potion. Carry the potion through the entire stage, and rather than go through the door, you can jump on the last whale's tail and jump over a small gap to find a vase. Now drop the potion, enter the door and go down the vase.

Warp to World 7-1
Go to world 5-3 as Luigi. After you climb the first ladder, power jump (hold down until you are glowing) on to the platform you normally can't reach. Pull up the plant on the right side of the warp pot. Throw down the bottle and go through the door. In the dark world, jump on top of the pot and go down. You should see the screen wiggle and it will say warp world 7 on a screen with Birdo.

Yoshi Challenge & Finding Yoshi Eggs
After defeating Wart in World 7-2, you unlock a special Yoshi Challenge game on that file. It allows you to replay any stage in search of two Yoshi Eggs. Unfortunately, it gives no description of the kinds of areas the eggs could be hidden. The eggs are hidden in Subspace, but the searching for the egg is the challenge. Also, if you lose a life, you lose all of your eggs as well.

Yoshi on the Title Screen
To get Yoshi on the title screen, beat the game on Yoshi's challenge and instead of an egg,there will be a Yoshi.

You'll love this Super Mario Advance ad: