Life in Hawaii can be fun if you have your friends with you and you spend time together. Today Stitch and his experiment friends decided to play baseball. Because everyone loves this game, they want to prove that it does not matter that they are a bit different on the outside, but they can play usual games and actually be good at it. Therefore, a Cosmic Slugger game would be the perfect occasion to show this to everyone. To take part in the fun, all you have to do is help Stitch hit the ball that comes to him as hard as you can. To do that, move Stitch with your mouse and keep your eyes on the ball. When the ball is getting closer, hit it with the middle of the bat to make it soar. To pass a level all you need to do is reach the target number of home runs and there you are! You will be able to challenge another experiment and play with more and more friends. Try to gain as many points as you can by hitting the ball in the right way. Gather more points and use them to boost your skills by using the Power-Ups button. Doing this thing, you will be able to become better and better until you will be the best at this game. So what else are you waiting for? Get your bat and start confronting your friends in the coolest baseball game you ever played!
- This game is very similar, if not identical, in gameplay to the much more infamous Winnie the Pooh's Home Run Derby. There are a few differences between the two (outside of the theming and characters).
- Cosmic Slugger features unlockable baseball cards of Stitch that can be printed.
- The level selection for Winnie the Pooh's Home Run Derby allows players to view all the stages they've unlocked at once and choose from there, although stages that are not unlocked yet will be completely hidden. Cosmic Slugger only shows one level at a time, and players must use arrows to select a level, although locked levels can be previewed with the names and silhouetted heads of the experiment pitchers visible for each one.
- The upgradable stat systems between the two games are different. Winnie the Pooh's Home Run Derby has stats for batting power, contact, and movement speed, and each of them can be upgraded from Level 0 to Level 20. Cosmic Slugger drops the movement speed stat altogether, making Stitch move as fast as Winnie the Pooh at Level 20 in the latter's game, and only has three upgradable levels for contact, although to make up for the reduction of, upgrades for that stat are much more expensive from the outset. Upgrades to the bat contact also changes the bat and Stitch's uniform, unlike in the Pooh game where the title character always wears his iconic red shirt and holds a wooden baseball bat regardless of upgrades.
- Players can exit a game in progress in Cosmic Slugger at any time, allowing them to restart a level sooner. Winnie the Pooh's Home Run Derby has no such option, forcing players to play the whole level until they're done before they can restart.
- Ironically, despite being a Lilo & Stitch baseball game with the word "Slugger" in its title, Cosmic Slugger does not feature the experiment Slugger at all.
- Clyde's bionic arm is changed from his left arm to his right arm.
- Yin is colored green in the game instead of her normal tealish-blue.