Big Boo's Haunt: The final world, Mansion. Appropriate considering Pac-Man's main enemies are ghosts.
Blackout Basement: Crisis Cavern has a few sections in which the lighting dims considerably.
Canon Immigrant: Professor Pac-Man (from an unauthorized game from Bally Midway) finally makes his appearance in an official Pac-Man game. Sourpuss (from the Hanna-Barbera cartoon) makes his cameo in this game, too.
Clown Prix. Forget about pressing X in order to accelerate. That button is used to brake here. Okay, Chocobo Racing did it too, but at least it had the decency to use another button, the square (no pun intended) - arguably even worse given most games use the square to brake.
But the worst offender is the pause menu, where choosing "resume" with X results also in a perceived pression of the button outside the menu, and therefore Pac-Man will jump. And given the abundance of the Bottomless Pits, that would not be a good thing.
Camera Screw: The camera is suited just fine for a 2½D side-scroller, but given that a lot of level segments require Pac-Man to move not only left and right, but forth and back as well, it can make many jumps much harder to accurately judge. Most notably, are some of those wheels in Spin Dizzy far away, or just really small?
Heroic Mime: Pac-Man, though at the beginning he yells when he sees that his friends and family have been kidnapped.
Hilarious Outtakes: If you beat the game at least once, you'll unlock a set of outtakes that are pretty funny.
Lock and Key Puzzle: Much of the game is finding the right fruit to unlock doors to progress or find secrets.
Meaningless Lives: This game may be Nintendo Hard in many respects, but let it never be denied that it is ridiculously easy to amass a life count in the hundreds. Getting three Galaxians at the end-level slot machine nets you three extra lives, and on average you can play the slot machine five to ten times per level. Memorizing the order of the slots is easy, because all three use the same pattern; in fact, if you regularly play in earshot of others, they might start to be convinced that "apple-cherry-peach-cherry-STOP!" is your new Madness Mantra.
Milestone Celebration: Pac-Man World was released on the 20th anniversary of the arcade game, and the third game on the 25th. In fact, the first game's plot revolves around Pac-Man's friends getting abducted right before his birthday party.
Mirror Boss: Toc-Man, the Big Bad of the game, who utilizes one of Pac-Man's techniques in each of its attack phases.
Arc Words: Pac-Man is often told that everyone in Pac-Land is counting on him.
Bottomless Pits: The farther you go in the game, the more terrain becomes composed of nothing but thin lines and platforms surrounded by deadly elements such as pits, lava and freezing or grimy water. It's a huge part of how this game can be so difficult.
Camera Screw: The camera will often refuse to turn at certain moments, even when it obstructs the next platform you need to get on.
Chainsaw Good: Treewood Forest and to a lesser extent Butane Pain has circular saw blades as common obstacles.
Every 10,000 Points: An extra life is awarded for achieving 25,000 points in a level. This becomes a Game Breaker in some levels (Haunted Boardwalk being one of them), since doing well in mazes can easily lead to a total of more than that amount, and the points are added to the score every time you respawn at the maze checkpoint. In other words, if you surpass 25,000 points after a maze, you will never lose a life until you either beat the level or stop at another checkpoint.
Go for the Eye: A variation on the one above; to defeat the big submarine in "Whale on a Sub," Pac-Man has to shoot the four stern propellers - while avoiding the mines the sub "poops" in your general direction.
Green Hill Zone: The first world, a meadow region referred to inexplicably in the manual as the "Forest."
Guide Dang It: Some fruits/tokens are hidden in really obscure places you wouldn't think of looking, but Night Crawling in particular has an egregious example, one of the apples is hidden inside a bat hovering around hellevator platforms over a bottomless pit, most people wouldn't be crazy enough to try and kill that particular bat(trying to flip-kick them is a real pain in the ass)
Heroic Mime: Pac-Man again, except in some versions where he comments on the bosses' weaknesses.
In Case of Boss Fight, Break Glass: Inky and "Clyde" are defeated this way. Pinky also has a glass hitbox that shows cracks and deformation as she takes damage, but the player can't actually reach it.
Many checkpoint sections have more than one extra life for which the surplus can be abused, but the best one is the secret area in Butane Pain, which can give eight one-ups for the price of one!
Blade Mountain is incredibly generous on lives. Not so much the first time through, but normally when a token is collected on one visit, every revisit will replace it with a health wedge. Blade Mountain has a few crates that hang in mid air, but instead of being replaced with health wedges, they're replaced with LIVES. You're forced to open most of these crates too, so you can potentially gain thirteen lives on one visit. Very few are hidden for the most part.
Law of 100: For every 50 Pac-Dots you collect, you regain a health wedge.
The Last of These Is Not Like the Others: Played straight with the whale-shaped ocean boss, but inverted earlier on; Blinky, Inky, and Pinky all pilot giant robots shaped like ghosts. Clyde pilots a giant robotic frog.
Lock and Key Puzzle: Fruit chests are nowhere near as prevalent as fruit doors from the previous game, but they serve the same purpose.
Nintendo Hard: 100% Completion requires very skilled platforming to collect everything compounded by the screwy camera, the precise jumps required, and one-way levels such as Blade Mountain. In addition, Time Trials have strict upper limits for the Bonus Token reward and of course, dying at any point is an instant failure. Of course, the requirement for unlocking Ms. Pac-Man is nearly every token, which means you have to complete most of the challenges to play it in the game.
If you had a release that was pre-Greatest Hits/Platinum Hits/Player's Choice, the game was even harder. The ghosts killed you in one hit, the platforming was more dangerous, and the power-ups didn't last as long. Games do go through revisions from time to time, but very few are this notably different from each other.
Timed Mission: A sidequest for each non-boss level, available once you beat the level normally. All checkpoints disappear, but you don't lose extra lives for dying. Also fruit and extra life pickups are replaced with clock that freeze the timer for two and four seconds, respectively.
Flawless Victory: Blade Mountain's time-to-beat is 62 seconds. The only way to achieve 61 seconds is by collecting virtually every clock and never taking damage once.
Advanced Ancient Acropolis: The Ancients, who built many of the ruins that a few levels take place in. They were destroyed when their lust for power drove them to try and siphon energy from the Spectral Realm. Erwin's big plan? Do it right this time.
Bash Brothers: Pac and Clyde(Blinky) towards the game's end, full-stop. While it starts as obvious Teeth-Clenched Teamwork, the two end up manning the same mecha to take down a literal army and generally spending the rest of the adventure tagging out with each other to dish out punishment.
Darker and Edgier: Compared to the rest of the trilogy. The levels have a much more gritty feel in this game, and Erwin is the most evil Pac-Man villain to date, with the fate of both Pac-World and the Spectral Realm hanging in the balance.
Good Old Fisticuffs: Pac finally puts those boxing gloves he's been wearing for twenty-five years to proper use.
Gotta Catch 'Em All: The trading cards. One can be found in each level, and you can get another by collecting all of one type of fruit in a level. Unlike World 2, however, Pac-Dots just add to your score and are not required.
Mini-Mecha: The new Toc-Man, described by Orson as being "15 tons of the most state-of-the-art bad guy-smushing technology ever balanced on legs". When Clyde's in the copilot seat, it gains a sonic scream cannon.