Last night, I beat the 99 levels of Bubble Bobble (NES) by myself, without using an umbrella. I did get the special items that turn the level into a bonus round, blow up all the enemies, or bounce around helping with them on a handful of levels though. It may have taken two hours on the levels. Definitely took a lot of lives, especially on certain later levels.
Then, the final boss was this super hard huge guy with 60 life that flies and throws ham. I had played him briefly recently when a friend had used a code to get to him. He said it was the hardest boss. I didn’t beat him, but I figured out some tricks, and was able to get him down to 33 once. I probably spent another two hours just on him.
My console froze soon after, and it was after 3 AM, so I stopped. There wasn’t a password to get back to the boss, but I did remember the password for level 97, ‘GGEEB’. That will give me a little warmup before I try again against the boss. Of course, some of those late levels took me quite a while.