Released in late 1983, Jr. Pac-Man was the last arcade Pac title developed by General Computer Corporation and released by Midway. It does away with the side tunnels (not unlike the Japanese developed Pac & Pal, which released the same year) but now features giant "double-wide" mazes that scroll horizontally left and right. The bouncing bonus fruits (now mostly toys) transform any pellets they touch into slightly larger, more colorful dots worth additional points at the cost of slowing Junior down, and the ghosts are now more aggressive and no longer "scatter"- instead opting to always chase after Junior, applying constant pressure.
The game's story follows Junior as he meets and becomes smitten with Yum-Yum, the daughter of Blinky, the red ghost. He gifts her a balloon in a later intermission and finally the star-crossed lovers "escape" in what I personally think is the most confusing intermission out of all the arcade Pac-Man games. Blinky approaches Junior and Yum-Yum before Ms. Pac appears and within a fraction of a second Blinky immediately diverts his attention from the young couple and starts chasing after Ms. Pac. Junior and Yum-Yum run off but uh... what about your parents, kids? What if Blinky chomps Ms. Pac, or Ms. Pac chomps Blinky? I guess I'm putting too much thought into it but it's a very weird and "sloppy" feeling cutscene.
Jr. Pac was not a huge success. It didn't have the same cultural impact as Pac or Ms. Pac and it launched when arcades in general were experiencing a downturn. To make matters worse, it's hard. Too hard. From a game balance perspective Jr. Pac is a goddamn mess regarding difficulty. Each stage is considered two in terms of difficulty- whereas Pac and Ms. Pac scale difficulty in ones (stage 1 is difficulty 1, stage 2 is difficulty 2, etc.), Jr. instead scales most of them in twos (stage 1 is difficulty 2, stage 2 is difficulty 4, etc.) Add on to that the changed ghost behavior (lacking scatter) and the player literally never has a chance to stop and catch their breath. The ghosts are always, always in constant, aggressive pursuit, and there's no tunnels to escape through. Power pellets last a laughably tiny amount of time- by stage 2 it's immediately apparent when the ghosts begin to flash only a couple seconds after they turn blue (it seems around 5 seconds total is all you've got in the second stage, and it only gets worse from there). Whereas Ms. Pac felt balanced and approachable to players both new and old, Jr. seems catered strictly to Pac-omasochists. It doesn't help that the default setting for extra lives is... well... none. The game's stock extra life setting is zero. You get one shot, if you die it's game over.
Jr. Pac isn't a common candidate for hacks. It's code though is largely built on top of Ms. Pac-Man, meaning it doesn't seem too difficult to poke around. It's data is stored in 5 8KB eproms, which can be split into 10 4KB files for easier comparison with the preceding Pac games.