Pac-Man - Did You Know Gaming? Feat. Guru Larry
In the original arcade build of Pac-Man, there is a specific area on the board that can be used as a hiding spot where the ghosts cannot see you. To access it, enter the upward tunnel, located just to the right of where Pac-Man spawns in on the board, from the right underneath, and keep Pac-Man facing up (do not do this as your first move when the level immediately starts, move slightly before trying this, for instance looping around the small left pathway from where Pac-Man starts and then going to the hiding place). This exploit can be used the same way on every level in the game except for the Strawberry level (the second level of the game). The Strawberry level has a slightly different way of pulling it off that can only be done there, requiring you to enter the same tunnel, but entering it while traveling left towards Pac-Man's spawn spot instead of entering by going to the right.

The A.I. for the ghosts works in two different modes, Chase and Scatter. The ghosts start in Scatter and aim for their own corners of the board while ignoring Pac-Man. In Chase mode, they can see and will actively chase Pac-Man. The ghosts will alternate between scattering and chasing Pac-Man in set intervals, and after the fourth Scatter, they will chase Pac-Man until you die or win the level. Due to a programming oversight, the ghosts cannot travel up in the "T"'s above and below the ghost spawning area, forcing them to move right past you. The ghosts also have unique methods of targeting Pac-Man, and all of this info put together allows the hiding spot to be possible. However, there is one exception to this trick. When Blinky switches from the fourth Scatter back to Chase for the rest of the level, he will come down from the top-right corner of the screen, and it is possible for him to enter the tunnel from the right entrance and kill Pac-Man, making it crucial not to perform this trick right before the fourth Scatter switches back to Chase to avoid the risk of death.

This exploit was patched out of future ports of Pac-Man, although ports containing the original arcade build will still retain it.
Contributed by MehDeletingLater
Whenever a ghost enters a side tunnel, its speed is cut nearly in half. They also slow down when they are frightened which then, for the first four levels, Pac-Man speeds up.
Contributed by Stryker94
For the fist 20 levels in the game, modifications are made to Pac-Man's speed, as well as speed and behavior of the ghosts. Once the player reaches level 21, no further changes are made, and every level onward plays identically.
Contributed by Stryker94
Whenever Pac-Man eats a regular dot, he stops moving for one frame (1/60th of a second), just enough time for a following ghost to over take him.
Contributed by Stryker94
The 4 ghosts in Pac-Man all have separate programming on how they chase Pac-Man through the maze. Blinky (red) is the chaser and will chase Pac-Man around the maze as well as speed up depending on how many dots are left on the maze, Pinky (pink) is the ambusher and tries to get ahead of Pac-Man, Inky (blue) is very unpredictable as his path is calculated using Blinky and Pac-Man's location, and Clyde (orange) is the coward and will charge Pac-Man if he's far away but runs when he's close by.
Contributed by KidDivinegon
It's believed that Pac-Man's design came from a pizza with a slice removed. According to the game's designer, Toru Iwatani, this is only half true. The other half of the design comes from the Japanese character for mouth, kuchi (口), which he rounded out to make it into a featureless ball. An idea to give him eyes was brought up during development, but was dropped to make sure Pac-Man wasn't over complicated.
Contributed by gamemaster1991
Pac-Man's name was changed from Puck-Man because arcade operators feared vandals would alter the letter P to F on the arcade machine.
Contributed by Outofmind23
Pac-Man contains a kill screen on level 256 in which the right half glitches into a jumble of letters, numbers, and symbols, caused by a programming oversight in how the fruit is drawn to the screen . The level is actually still playable, though the right half does not behave like the left.
Contributed by ThisGuyInTheSuit
Near the top of the maze, the large rectangular walls are not solid, but rather hollow, as proven by altering the palette of the maze walls. By default, they appear to be solid as both the background and maze interior colors are identical, and because of this, wall tiles without boundaries were never inserted into the game.

Certain bootleg versions of Pac-Man, such as JoyMan and the Galaxian hardware version show this in full detail.
Contributed by Superjustinbros
In the second of the three intermissions, when Blinky's coat is ripped off, you can see Blinky's eyes temporally change from their standard blue to black. This is to allow the game to draw Blinky's foot with a proper skin color, as each sprite could only have four colors, including a transparent (black) color.
Contributed by Superjustinbros
It took almost twenty years, but on July 3, 1999 for the first time ever, a perfect score of 3,333,360 was achieved on Pac-Man by Billy Mitchell at the Funspot Family Fun Center, Weirs Beach, New Hampshire. To achieve this, Billy had to eat every single bonus prize and every possible blue ghost in all 256 levels of the game - a feat which took him over six hours to complete. Not only that but he didn't lose a single life. It was the first ever perfect game of Pac-Man.
Contributed by Grey Fox
Pac-Man was created to appeal more to girls; the game's creator noticed that women enjoy eating desserts, and designed the game around eating things. The game's original name was "Puck-Man", which can be translated to "Munch Man".
Contributed by DidYouKnowGaming
When Pac-Man was being developed, the game's creator Iwatani says he was pressured to make all the ghosts red by the president of Namco. Iwatani refused the order, and on a questionnaire for game testers, asked if they preferred single color ghosts or four colors. Not a single person wanted the red color option. This convinced the president that she was wrong.
Contributed by DidYouKnowGaming