I had a run where I finally found the combo of the laz0r + chocolate milk. Pretty much the most OP setup in the game since you can shoot a wide, infinite pierce one-shot kill beam across the room. Since most rooms have the enemies spawn in a clump or line in the middle I would often kill everything in 1-2 shots and barely have to stop moving (the most satisfying was a huge line of leapers). Another little benefit was being able to shoot the explosive barrels through the mob to just kill everything.
With that + the BoB I ONE SHOTTED the worm boss in Womb 1. I killed Mom 1 in 20 secs (usual: 40), Mom 2/It Lives in 33 (old best, 1:03). Great for those bosses because the enemies can't block the damage.
For Mom II/It Lives, does she never go away as long as you leave all the enemies alive? I pretty much go in guns blazing but maybe that's the slower, dumb way.
I think Mom II has two phases: one where she spawns enemies, hangs around for a moment, then goes away until you've killed them all, and in phase 2 she just stays around all the time while spawning enemies. But I might be wrong.
The guess about Mom's Heart is correct; if you don't kill the enemies in the fight fast enough, she'll run away. If you can get piercing shots and be lined up from the left/right, however, you can pierce through all the enemies she summons at once, meaning they're dead too fast for her to retreat - in addition to still being wailing on her. It's the fastest way to kill her.
Also, I doubt any shot upgrades affect Dr. Fetus, but I can't be sure.
I don't know about the special ones (Technology, Number One, Chocolate Milk), but I do know that damage and tear upgrades directly affect it, pretty much in the way you'd expect it to. Oh yeah, and getting the Bomb Upgrade upgrades it as a regular shot as Dr. Fetus, so whoooo more power!
I dont know if this bug will be fixed but something to point out. I think it is announced to be fixed or something.
but say you have a Lord of Flies Boss, and you kill him. If you somehow "leave the room" while there are still normal enemies for every time you leave the room and kill 1 enemy another item will spawn on the pedestal. I've accidentally gotten like 4 items this way from one boss...
of course this might be a unique situation w/ the CAT lives powerup. where i kept accidentally hitting flies =_=. but i'm pretty sure if you can work it out, it'll work.
Another way to leave the room would be the different teleport options such as the cards or the teleporter itself. I'd have to test to see if you can blow the door open to leave the boss room, now that they've fixed that, I'm not sure one way or another. That could be really useful if that is the case, but it depends on the extent of what triggers the extra items on the pedestal. I'll try it out in a bit if I can get Lord of Flies to appear.
Edit: Wow, Lord of Flies was the first boss I got in my test attempt, but I had no way to teleport out of the room. Bombs don't blow open the boss door, so teleporting will be required for futher testing.
They took some of the exploits out, including the Doctor's Remote one, which works similiarly to what you are saying. They probably will take it out Halloween update if not already have.
About Mom's Heart, you can also use bombs to take out the summoned enemies before she retreats. Obviously, it doesn't always work on It Lives, since that will summon bosses.
Minor bug: The guys with their brains out can pathe into bombed doors and get stuck there, making them easy to kill. Perhaps other mobs can as well. Not a massive help, but who knows.
Yeah; exploits which clone boss item drops have been removed. Sadly.
I can't help but wonder if Dr. Fetus might not be the best shot upgrade for speed. It replaces your normal shots with bombs; which sounds a little unwieldy (and okay technically it is), but it's basically an infinite supply of bombs to blow open doors and lets you more or less ignore combat.
The fact you can do that (blow open every door, kill minimal enemies), means all you have to worry about are Bosses and the rooms before that, so a total of 8 bosses + 8 rooms of enemies. It far outweighs it, really. But of course yeah that means you have to become used to wielding the bombs as tears. Granted once you do get a grip on it, the game becomes easier and the running begins.
The thing is though the chances of finding it early on in a run + having good luck with the path is really small. Maybe you could use Isaac's dice item to help out.
I've found Dr. Fetus in the Basement 1 item room about four-five times, so it wouldn't be too much of a stretch to reset continuously until it shows up, considering how much of a timesaver it is. As for character choice, I'd say Cain because his higher initial speed will save time over the others, since we don't need Book of Belial if we really are going for this.
I've been doing runs for like 25 hours and have seen the Fetus maybe twice. Also, I had a situation where the game was unbeatable because I had to go through a room in Depths 1 filled with bombable rocks but I had no bombs. Didn't bother me much because the run was pretty mediocre, but kinda amazing.
Had a run where I used the beggar card during the depths 1 boss, fed it coins while fighting, and it gave me a BIBLE! :O Too bad I died on Depths 2. This game depresses me.
I'm thinking it's worth making a small detour to the shop in depths 2 to hope for a Bible, I've seen it pretty often. Only if you actually have 15 coins at that point, of course. If you have enough damage upgrades it becomes much more valuable than whatever item you have at that point. Mom is just so annoying ._.
Yes, the Dr. Fetus item is where it's at. I set a new PR for getting to Depths 1 (4:10 vs. old 'perfect' 4:30 with Judas) despite taking several wrong turns. I use Isaac for the dice item + his health is nice too. Cain does walk faster but the dice saves you from going crazy since it still takes a lot of dead runs before Dr. Fetus shows up. Plus you can use it to manipulate the rest of the treasure rooms and maybe get something sexy like the Necro or Monstro's Tooth or...a Bible? I don't know if I've ever seen one of those in a treasure room.
The way the bomb bounces off things confuses me sometimes, plus I hate killing flies with them. It's frustrating when enemies push the bomb away from the door you want to blow up. A useful tactic is to put a bomb right next to you (as you're standing against a wall or obstacle), wait for the enemy to rush to you, then run away before the bomb blows up and hopefully it'll die (useful for melee enemies that charge). Dr. Fetus makes the bosses that jump around a bit more difficult (and Mom 1), although it halves the time to kill them if you hit every single bomb (I've been keeping track of times for nearly every boss). It ROFLSTOMPS the Grub boss because you can keep kicking bombs right into its mouth.
Chocolate milk makes your bombs chocolately and you can charge up but it doesn't change the bomb at all. I wonder what lazor + bomb does.
Had a successful Dr. Fetus run, ~13:47. Might make a video of it later but I can do better and I learned a lot. Had to get used to avoiding enemies while kicking bombs at doors instead of killing enemies. Always a question in a room with lots of doors whether you should kill the enemies or just move on. If you have to come back killing them will save time. If not, killing them will waste time. But if they're easy to kill I think it's worth it. My least favorite involves rooms with fast zombie things since they push bombs a lot and I almost always get hit.
Milestones: Depths 1 (arrival) = 5:31 Mom 1 = 8:40 Mom fight = 47 secs (sloppy but Dr. Fetus is frustrating to me for this fight) Womb 1 = 9:34 Womb 2 = 10:27 Mom 2 = 13:01 Mom 2 Fight = 45 secs
So with better pathing I could get ~11:47. A Bible for the Mom fights would save like a minute and a half, assuming I didn't have to go too much out of the way to get it so...10:17ish? That'd be pretty crazy.
Another nice thing about Isaac and his D6 is you can use it on the boss treasures too. So if they give you useless Mom range items (e.g. Mom's panties, lipstick, heels) you can change it to a health item usually. This doesn't work on theme items, like the horsemen always give meat cubes and the D6 will just change it to another cube. Ditto for the Gish Monstro fight and I assume Steven.
Yes, Mr Mega does buff up your Dr Fetus bombs. And marshmallow, with Dr. Fetus and Mom 1, I've discovered a good strat is to stand in the middle, let the foot come down, then right after it comes down throw a bomb at one of the eye holes. Kind of luck based, but it's a hell of a lot more reliable than trying to hit the foot.
Yeah, Mr. Mega does affect Dr. Fetus, by making the damage even more ridiculous. I mentioned this in my first post, where I said an optimal run would be Dr Fetus, Mr Mega, and the Shovel.
Plus as for clearing rooms vs running through them, a lot of times the enemies will be nicely grouped in the center so you can take them out with one bomb right away.