So, the hero has found the giant factory belonging to the Big Bad. He enters with his True Companions and finds weapons that could kill thousands or maybe even millions, all built by and being built by the locals. While the hero believes that the locals all knew about the Big Bad's plan and were helping him willingly, a few questions from The Heart clears up the matter — the locals simply think the weapons are harmless machinery that will be used for building houses and/or farming.
This trope describes situations where somebody uses someone to make or do something by lying about what exactly it is that they're doing, or assuring them that it's for the greater good. It could be something as simple as stealing plans or moving an item to another location, or something major, like building a Doomsday Device or breaching a boundary — if the Big Bad plays on their ignorance to make them do something; it's this. This can often result in a HeelFace Turn or My God, What Have I Done?. See also Evil Plan, Nice Job Breaking It, Hero!, Awful Truth, Redemption Equals Death and Ambiguous Innocence. Characters made of Ignorance Is Bliss include the Noble Savage.
- In Infinity Train: Blossoming Trail, Trip brings up this trope in regards to making sure Goh never finds out about the Infinity Train, noting that due to how Goh can be very obsessed with things (Pokémon, Mew and Ash) that if he becomes obsessed with this knowledge, he'll try to enter the train and thus there will be two children stuck on the train.
- Diamonds Are Forever:
- Blofeld kidnaps Willard Whyte and uses his industrial empire to build and launch a Kill Sat. Only one other person in Whyte's organization knows what's going on: the rest are kept ignorant.
- A rocket scientist helped Blofeld to build the Kill Sat because he thought Blofeld would use it to help achieve world peace. Of course, this wasn't the case.
- At the start of Van Helsing, Dracula tells Dr. Victor Frankenstein that he provided Victor with a castle and lab equipment, not for scientific advancement, but because he wanted to use Victor's creation for his own ends.
- In American Gods Wednesday uses Shadow to start a war between the gods so they can conquer the new gods, when in reality, Wednesday and Loki just want the power they'll gain from a field of dead gods.
- The Belgariad: Errand is brought up to be totally innocent so he can sneak into the Rivan throne room to steal the Orb, without knowing what will happen afterwards. It turns out to be a subversion - Errand, or rather Eriond, is a God in Human Form who doesn't know it, which is why he can touch the Orb unharmed. He's guided by the Light Prophecy, who places him in Zedar's path at exactly the right moment as the start of a very long game.
- Star Wars Legends: The Jedi Academy Trilogy reveals that the lead scientist responsible for designing the Death Star and Sun Crusher has no idea that they were used to destroy inhabited planets and star systems, believing them to be intended for large-scale mining projects. Justified in that she was brutally conditioned as a child to take a For Science! view of her work and not think beyond it.
- Harry Harrison's The Stainless Steel Rat. Jim diGriz discovers that the government of the planet Cittanuvo is building a Warlord class battleship under the pretense that it's just a transport ship. After investigating, he finds out that two elite criminals tricked the government into building the ship with the intent of stealing it and using it for interstellar piracy.
- The Howlers in Animorphs routinely wipe out entire species at their master's command so the protagonists assume they must be consumed with rage and enjoy causing destruction. It turns out they think it's all a game.
- Ender's Game, because when he goes to the simulator he's actually commanding real troops.
- In Glee, Sue gets Brittany to give her the set list for New Directions, but Brittany has no clue about what she's going to do with it.
- NCIS: In 6.21, "Toxic", Abby builds a biological weapon without knowing what it is.
- In Dollhouse, it turns out the Evil Corporation is building a Doomsday Device by making each of their research departments around the world build a little part of it, and nobody knowing about the larger picture.
- In season six of Supernatural, we see Castiel take on the souls of Purgatory, without having any idea of the consequences. It is later revealed that he has taken on millions of Leviathan souls, who later become a Big Bad.
- Spyro: Year of the Dragon: Bianca helps the Sorceress abduct the dragon eggs thinking they'll be raised in the Forgotten Worlds, which will stop all magic disappearing from her home - the Sorceress really plans to kill the dragons and take their wings for a spell.
- In Metal Gear Solid, Otacon designed Metal Gear REX under the assumption that it would be used as a mobile TMD to destroy incoming missiles - he had no idea that his employers would arm it with nukes instead.
- This is probably the one and only Pet the Dog moment from Matt Engarde in Phoenix Wright: Ace Attorney - Justice for All:
Engarde: (Sigh)... I thought if you didn't know, maybe you wouldn't feel so bad for doing your job...
- In World of Warcraft Horde-players visiting Dragonblight are offered a questline to help the Forsaken gather ingredients for a plague that will inevitably wipe out the scourge, which Puttress later uses to kill, not only scourge-soldiers, but also the combined army of humans and orcs battling them.
- Fighter of 8-Bit Theater is an example of this. The other Light Warriors often get him to do things by convincing him it is for the greater good. There's also the fact that he still believes they're heroes after all the untold damage they've caused.
- The Inexplicable Adventures of Bob!: In an uncharacteristically manipulative moment, in her second appearance, Voluptua lets Bob fly off on what he thinks is a very simple mission, while she suspects an alien supercriminal just might be waiting for him.
- Cecil of Welcome to Night Vale cheerfully reports the obviously bogus coverup stories concocted by the City Council with little to no indication that he doesn't believe every word. Also, choosing not to question what one is told seems to be the only way to survive living in Night Vale.
"Ignorance may not actually be bliss, but it certainly is less work."