- Breather Boss: The Final Boss, Gantu is relatively easy to defeat compared to the first two bosses of the game.
- Catharsis Factor: After struggling to defeat 621, players will feel relieved that he is done for.
- Ensemble Dark Horse: 621 and Dr. Habbitrale.
- "Funny Aneurysm" Moment: An In-Universe example. 621's taunts seem funny at first, but when you attack his mutated form, it became less funny and more tragic.
- Goddamned Bats: The Buzzers, which are red wasps that won't stop attacking, even if their hive is destroyed.
- Hilarious in Hindsight: The film the game was based on happened to be released on 6/21/2002.
- It's Hard, So It Sucks!: The difficulty can be considered unbearable.
- Most Annoying Sound: Where do we begin?
- 626's sound clips. MOST IF NOT ALL OF THEM.
- "Who's superior now?"
- "Let's try it one more time. 621 good, 626 bad!"
- "You have enough DNA to continue if you wish."
- "Whatever you do, don't look up!"
- Most Wonderful Sound: 626 saying "Yee-haw" after you pick up Red DNA.
- Player Punch: During the first two sections of the game, once you get killed you hear taunts from 621.
- Scrappy Mechanic: The godawful camera.
- Special Effect Failure: The graphics are considered inadequate, especially for a PS2 game released in 2002.
- Suspiciously Similar Song: The first level's music shared similarities to a song from Shadow the Hedgehog.
- That One Boss: Mutated 621 can be a real pain for gamers.
- That One Sidequest: Following the Squid Bots can be a pain.
- The Problem with Licensed Games: It is the most ambitious of the tie-in games, being a prequel to the events of the film and also being one of the first works to introduce one of the other experiments. However, it was criticized for rough gameplay, camera issues, and weak graphics compared to other PlayStation 2 titles of the time. The events of this game were also later Retconned by the events of Lilo & Stitch 2: Stitch Has a Glitch.
- They Wasted a Perfectly Good Character: The Grand Councilwoman was going to have a role in the game, but she is only seen in a building advertisement in Piston.
- They Wasted a Perfectly Good Plot: The 700-series experiments are seen developed but are not seen in any other part of the franchise.
- "Seinfeld" Is Unfunny: The game had some praise for introducing a different experiment that isn't 626. But by a year later, it's not as revolutionary.
- Unintentionally Sympathetic: 621 had some hints because you can't help but understand why he gets upset about not being superior.
YMMV / Stitch: Experiment 626