Ms. Pac-Man

It's easy to mistake "Ms. Pac-Man" for a simple sprite-change of 1980s "Pac-Man" by Namco, but in fact that's not exactly true. "Ms. Pac-Man" is different. It wasn't even made by Namco.

Ms. Pac-Man Arcade

The story of "Ms. Pac-Man" starts with General Computer Corporation (GCC), a company made up by MIT-dropouts, and the so-called "enhancement kits".
In the early games of arcade gaming, arcade owners found that as players became more skilled at the games they could play for longer and longer without paying any extra money. Then along came "enhancement kits", essentially just a third-party mod of an already existing game, but with improved game-play and increased difficulty.
GCC started developing such an enhancement kit for "Pac-Man", named "Crazy Otto".
"Crazy Otto" was essentially "Pac-Man" but the character had legs and the ghosts where given antennas. Unlike "Pac-Man", "Crazy Otto" had 4 different mazes (unlike "Pac-Mans" 1), and the fruits (that works as bonus items) moved around the stages, instead of being right below the ghosts "pen".

"Crazy Otto", Atari 7800
(Actually a gfx hack of "Ms. Pac-Man". as "Crazy Otto" was never released)

At the time of development of "Crazy Otto" GCC settled a lawsuit with Atari over "Super Missile Command", which was a "conversion kit" of "Missile Command" (1980. Atari). Part of the settlement terms barred GCC from selling future conversion kits without consent from the original game manufacturer.
This obviously made GCC hesitant about "Crazy Otto", so they approached Midway, which was the distributor of Namcos games in the U.S. Midway had become inpatient in waiting for the next "Pac-Man" game, which would be "Super Pac-Man" (1982), and bough the rights to "Crazy Otto", making changes to the sprites in order to reflect the "Pac-Man" series.

"Ms. Pac-Man" (1981), Arcade

The name of the new game was changed multiple times during development, from "Super Pac-Man", "Pac-Woman", and "Miss Pac-Man". But as the third intermission showed the couple getting a baby, there was a fear of protests to the fact of the couple having a baby without being married, and so the title "Mrs. Pac-Man" was decided, and in the end "Ms. Pac-Man" was chosen because it was easier to pronounce. The three last name-changes all occurred within 72 hours of production.

Shortly before release Stan Jarocki of Midway stated that "Ms. Pac-Man" was conceived in response to the fact that the original "Pac-Man" was the first commercial video game to involve large numbers of women as players, and it was their way of thanking all those lady arcaders who had played and enjoyed "Pac-Man".

Changes from the original "Pac-Man" includes the change of the appearance of the main character, having a bow, lipstick and a mole.
Four different mazes, with different colors, and two warp tunnels rather than one (except for one of the mazes).
Fruits enter trough warp tunnels and move around the stage.
New music and new intermissions.
The intermissions show how Pac-Man and Ms. Pac-Man meet and eventually have a Pac-Baby.

"Ms. Pac-Man" (1990), NES

Reaching stage 256 causes an overflow bug, that causes the game to go black. However buggy code makes the game unplayable at stage 142.

If you are looking to buy a "Ms. Pac-Man" arcade cabinet you should be ready to pay between €600-€1.500 depending on condition and type etc.
For a nes version you could get away with €23 for a used copy, but for a brand new be prepared for closer to €270. (Funny how brand new nes games always seem to fetch such high prices)
For an Atari 2600 version you would have to pay about €4, and for a brand new about €9.