What are the dead-ends?
The game was known for having numerous dead-ends (i.e. getting into a state where the game could no longer be completed). When you get into such a state the game doesn't tell you - you can aimlessly continue playing.
Could someone supply a comprehensive list of all the dead-end scenarios?
Solution 1:
Note: this answer contains mild spoilers, but doesn't explicitly solve any puzzles.
In Maniac Mansion, the dead ends are essentially anything that prevents your characters from completing their scenario(s), and getting past Purple Tentacle into the lab.
Here are the general dead ends, which will fail the game regardless of your choice of characters:
Getting one kid stuck in the dungeon without the key, with none of the other kids being able get into the mansion
Killing a kid with an important item or ability (or perhaps an important status, such as having a character on your side), or only having one kid left when you need two to solve a puzzle. Obviously, killing any kid should raise serous concerns about your ability to finish the game
Killing the man-eating plant while you still need it
Using the paint remover in the wrong place
Being wasteful/careless with your dimes
There are also some actions that will prevent you completing one or more character's scenarios:
Exhausting the patience of the Meteor Police
Failing to develop the film correctly
Making the envelope unusable
Not collecting the package
Not collecting the stamps
Putting the wrong item in the envelope
Once you have gotten into the lab, there are no "dead ends" - the game will finish one way or another - but you may not have picked up some items you need to finish with a good ending. These items can be collected at any time before entering the lab though.
Solution 2:
Maniac Mansion is one of the few LucasFilm/LucasArts adventure games to have dead-ends.
The following are the ones I can think of:
- A character is killed while holding an item you need to complete the game, such as the glowing key before opening the outer lab door.
- Using the paint thinner somewhere other than on the paint blotch in the Study.
- You only have one character left alive and haven't completed the puzzles that require two people (draining the pool, getting the keycard, etc...)
- Use the wrong code on the Steel Security Door and then save the game... or use the hidden control panel for said door at all in the NES version.
- Drain the pool and save the game without enough time to refill the pool.
Solution 3:
From the point of view of a gamer looking to play Maniac Mansion for the first time, and worrying unknowingly making the game unwinnable, I think this is the most general, spoiler-free advice you can give:
Most of the characters have a special talent, and this talent is the key to completing the game in a specific way. Reading each character's description at the start provides some clue as to how they might (or might not) be useful. Only two characters have no special talents, so whoever you choose you will have at least one person you can win the game with.
Be wary of damaging anything in your inventory or wasting it where it accomplishes nothing.
You don't need to kill anyone/anything.
For some more specific advice, I would say the safest way to play is to take Bernard with you. His scenario is probably the hardest to accidentally lose, and if you do fail it, you will probably know. For a more interesting time, maybe try your other character's scenario, and you will have Bernard's to fall back on.