To get to the credits, you have to complete a series of mini game stages and their boss fights:

• Wario Introduction
• Jimmy I
• Dribble & Mona & 9-Volt (three stages that can be completed in any order)
• Jimmy II
• Orbulon & Dr. Crygor & Kat (three stages that can be completed in any order)
• Jimmy III
• Wario Final

The key to this speedrun is optimizing your menuing and restarting (on a GBA, A+B+start+select performs a soft reset) to skip various cutscenes. In WarioWare Inc, each time you begin a stage, there's a cutscene that can be skipped with a soft reset. Each time you defeat a stage/boss, the game kicks you out to the stage select and runs a simulation of a loading bar, which can also be skipped. The timing starts when you choose between male and female genders, and ends when you lose control of Wario as he dives under the wall at the end of the Wario Final Boss Fight.

So, the way that the soft resets should work are:

• Start timing. The game goes to a black screen, and the cutscene for the Wario Introduction starts, although not immediately. You have to soft-reset before the game says "DIAMOND CITY - 200X", but not too soon that you won't skip the cutscene. At this point, after the soft reset, when you enter into the Wario Introduction stage, you can mash the A button to skip right to the first mini game.
• At the conclusion of the Wario Introduction Boss Fight, the instant that the mini-game number cycles up once on the screen (here, it'll go from 9 to 10), you can soft reset, press start on the title screen, and immediately soft reset to skip the loading bar. Then, you'll go up and choose Jimmy I, and immediately soft reset after choosing Jimmy I, so that when you go select Jimmy I a second time, you can mash A to skip directly to the mini games.
• You'll repeat this after each Boss Fight: wait until the mini game number goes up by one, soft reset, press start at the title screen, soft reset, press start at the title screen, select the next stage, soft reset, press start at the title screen, select the next stage, and mash A to skip the cutscene and start the mini games.

The primary randomness in the game is in both the order and selection of mini games in each stage. Some stages are pretty fixed and the order of the stages is all that changes, but since the mini games are all similar lengths, the splits for these stages will be similar from run to run. The Jimmy II and especially Jimmy III stages have more randomness since they can pull from the entire group of unlocked mini games. If you get a lot of stages from Orbulon's mini game pool, your Jimmy III stage is gonna be slower. Bummer.

Losing at individual mini games only loses a small amount of time, mostly to the animation that plays showing you've lost one of your four lives you get per stage, and this time loss is dependent on the stage.

The key to this run is to learn the mini games, especially at the higher levels you might see in the final Jimmy III and Wario Final stages. Once the mini games are understood well enough, then you can focus on the boss fights. Here are my tips for the boss fights

• Wario Introduction: Sparring Wario There's not much too this, although you can press punch earlier than you think, so test the timing.
• Jimmy I/II/III: Punch-Out Each Jimmy stage features the same boss, although with more health and the ability to throw a stronger punch in the Jimmy II and Jimmy III version. This is a simple version of the NES game Punch-Out, where you dodge when the boss telegraphs that it will throw a punch, and then punch yourself. In Jimmy II and Jimmy III, the stronger punch has a different timing, and you can be knocked out (requiring a redo on the entire fight, likely ending your run), so watch out.
• Dribble: Galaxy 2003 This is a pretty standard shoot-em-up featuring a few key moments. After defeating a few waves of enemies and quickly collecting the green power-ups to increase your ships number of lasers and add a shield, a black hole will appear in the center of the screen and a ball will slowly descend. When it moves halfway down, you can shoot the ball to bounce it into the black hole. Ideally, you want to do this in one hit by shooting it on the left side of the ball right as you are able to. I tend to drop to the bottom of the screen and line up left and right using the triple shot positions of the words at the top of the screen: when the right-most shot from your ship flies through the E in the word SCORE, you're more or less lined up.
• Mona: Nail Call You press A to pound a nail in, one hit at a time. You fail if you pound the hand on either side of the nail, or if you hit the same edge too far from the nail center twice. You can actually swing the hammer almost immediately after the game gives you control, but the timing is tricky. You can also hit the nail multiple times (2 is straightforward, three is possible) in a single hammer pass, but it's risky.
• 9-Volt: Ultra Machine This is a straightforward pitching machine, with the primary hope that you get a lot of fastballs instead of the slow arcing balls. Watch out that sometimes the balls will disappear as they fly towards the bat, which is especially annoying on the fastballs.
• Orbulon: Dungeon Dilemma This is perhaps the easiest of the mini games, with the only randomness coming from the individual words thrown in each round to choose from, and whether or not the correct word is top or bottom. In the final round, the words SUCCESS or FAILURE can be swapped, so this mostly just comes down to execution.
• Dr. Crygor: Alien Laser Hero Here you play a head with a laser defeating a big vase that drops rocks, that, if they reach the bottom of the screen, destroy the Earth. There's some randomness in the order that the rocks fall in each round, and how far some of them fall.
• Kat: The Frog Flap There's no randomness in this at all, this is pure execution. Watch the top runs to learn this.
• Wario Final: Wario's Adventure Most of the randomness is pretty limited here, but the key is trying to defeat the final square with the diagonal boomerang. You're going to want to throw it and hit the square at least twice, and I've been able to throw it and hit it all three times in one throw, which saves a lot of time. After that, know that you can still die if you touch the boss on the ground while it's dying.

Good luck!