I decided to create this topic as incentive for whoever wants to TAS this game on Arcade. I've been playing this game for a long time in Arcades and now on emulators and i know lots of tricks that could make the run fast.
I'll just write about the tricks and strategies i know.
Infinite Combo: it's possible to infinite combo with any character in this game and even with the Green Giant Robot. For the normal Characters you have to punch three times and after the third hit, quickly press back and forward and three hits again. I never used Frame Advance in this game and it would have to be tested for how many frames you have to press back before pressing forward again, but i know that the character doesn't have to face backward when you press back to cancel the last hit combo. This is a fast way to clean the stages and is the best strategy (as far as i Know) to finish the bosses quickly. Also, there's another similar strategy for infinite Combo that is keeping the character in the middle of the enemies hitboxes and pressing punch three times, turn around and another three punches, turn around and more three... For Sho/Ginzu his third attack is too slow, so the best option is using just two punches, back and forth and more two slices. It's possible to infinite combo using the Green Giant Robot if you keep pressing forward and the punch button in a way that the robot only attack with one of his arms. It would have to be tested how many frames you have to wait for the use of the same arm again, if he uses the other arm, the enemy will fall.
There's no need to kill all enemies on the screen for it to scroll to the right, in the first stage for example, if you kill the first enemy and pass the other two, the guy with the knife will apear and you can kill him and the other two that will emerge from the ground, so the screen will scroll to the right. If you manipulate the two enemies you left behind for it to stay back and off screen, you'll be abble to enter the Bank and go to the first Boss. It's probably possible to manipulate other enemies to stay back off screen for the screen to scroll in other stages.
I'll list some stage by stage comments and possibilities for one player (I use it in realtime).
Stage 1: For the first stage what i wrote above is the way i usually play, with the difference that i pass the first enemy and kill the other two because in realtime i'd have to be lucky for the enemies to be left behind and the screen to scroll for me to reach the boss. When i get to the Bank i hit the enemy on the Robot and get the robot for an infinite combo on the Boss. Unfortunatelly this boss is a bitch sometimes and he uses to block your punches but it's not problem with frame advance and luck manipulation. After killing every boss you can run to the spot where the character usually goes when the fight is over and save time but not having to wait for him to walk to the right place.
Stage 2: I think the best here would be to go to the end of the screen and try to join all enemies and kill them together, but if you don't kill the first two enemies, you'll have to wait for other enemies to apear cause they only apear if the two first enemies are dead (or left behind). When you finish the enemies, stay on the right side of the screen to jump faster in the hole (If you try jumping as the screen is scrolling to the right, the character will turn back and walk to the spot you would have to be. On the next screen, after some enemies are killed, it's possible to reach the boss and infinite combo him.
Stage 3: If you kill the first 4 guys with knives, the short fat and the strange tall guy, you can go to the end of the screen with the other two knivers and the two girls following you, but you'll only have to beat the Samurai to go to the other screen. After beating the Samurai, quickly run to the spot that triggers the area transition. On the next screen you just have to kill two enemies (IIRC) and wait for the last ninja to apear, so you can run to the spot that will triggers the Samurai and get to the Boss screen. On this boss you just have to infinite combo him and manipulate the Samurai for him not to bother you.
Stage 4: In the next stage just kill the guy and run to the right of the screen to activate the area transition. On the next screen manipulate the two enemies for it to be toghether and kill both. When you get to the Arena, it's possible to manipulate the enemies for less appear. The first two can be killed very easilly and if you manipulate luck here, the next enemies to appear will be the last ones. After killing all enemies, you can run and jump when the screen is going to open and you land next to the door triggerring the area transition faster. For the Boss here is almost impossible to infinite combo him in realtime, though it wouldn't be hard with frame advance and manipulating luck. Also, if you're using two players at least, a green giant robot will appear on the arena and you can take it to infinite combo the boss.
Stage 5: For the next stage i think there'll be some issue if you go for the fast time or decide to make some entertaining trade off. For each ninja that is killed, in the end of the stage you'll have to wait more while the points are calculated and added to your score, and if you beat the 60 ninjas, it will still have a 100 points bonnus to be added, but if you don't kill any Ninja, when you reach the end of the screen the character will just go to the other area. For me i think it would be better to see all ninjas dead and a good pose when the screen freeze in the end of the area, but if the TASer manage to find some entertainning way to play around here it would be nice too imo. Infinite Combo on the boss (Usually if you hit the same enemy with more then one character, he/she will fall, but you can use all your team to beat the Old Doctor and he will take it all. You can do it too on Scummocide.)
Stage 6: Nothing important to say about this stage, the same as the others. When you reach the final area of the stage, you don't have to kill all enemies to go to the boss, wait for them and infinite combo. In realtime i have go down every time i cancel the combo cause they keep going down till a certain spot.
Stage 7: Just run and scape from all Ninjas, i usually go to the top of the screen as barrels don't hit me there. In the next area, after killing/or anything else the enemies, run and jump when the screen is going to scroll to trigger the area transition faster. For the boss there's nothing new, just run to him as soon as you take control of the character and infinite combo him.
Stage 8: Just kill the enemies you need to to scroll the screen and keep going. For the next area of the stage, kill only the fat ones that will stay on the screen. If you have time, try to kill some that drop food and manipulate them to give you the best food. The Boss is a bitch and has the damn desperation move to fuck you. I think it's not possible to infinite combo them (never saw, but maybe with frame advance and luck manipulation...) but you can keep manipulating him/them and hitting them in some way that they don't fall to the ground. Maybe some damage here can save time for beating them faster, that's the purpose on making some food to stay on the screen.
Last Stage: When reaching the elevator, go to the right enough for it to start going up before killing the enemies. You'll fight the first Boss again, after killing him, move to the right spot to trigger the area transition. For the last boss i usually keep grabbing him, two punches and throw from one side to the other with just one player, but as i said before, you can hit him with all characters in the same time and he will not fall and you can kill him extremelly fast.
If the run is one player, if i remember correctly, Hoover/Baby is the character who inflicts more damage on the enemies. Also, for Jennety/Mack, if you kill the enemy with the knife and he doesn't fall off screen, you have to wait for the enemy to melt before the screen is released. The only way to prevent this from happening is killing the enemy with any kick or using the desperation move.