Playing With / Obfuscating Stupidity

Basic Trope: An intelligent character pretends to be less intelligent in order to fool people about how effective they are.
  • Straight: Alice pretends to be naive and unsuspecting so that Bob will not suspect she is investigating him.
  • Exaggerated:
    • Alice pretends to be severely mentally retarded so that Bob will not suspect her.
    • Alice successfully fakes Laser-Guided Amnesia, and she routinely drops the act whenever she's alone with her friend who is in the know, only to continue the act when someone else enters the room.
    • Alice pretends to be excessively unintelligent and intentionally talks funny, as well as pretending to know nothing. She also acts annoying and mimics Bob's sentences when given the chance.
  • Downplayed:
    • Alice is not very smart, but she exaggerates the extent of her stupidity.
    • Alice is smart, but she just feigns slight cluelessness or average intelligence instead of pretending to be outright stupid.
  • Justified:
    • Alice wants to appear less of a threat to Bob in order to lull him into a false sense of security.
    • Bob is expecting investigation and consequently wary of people who appear too smart, forcing Alice to downplay her intelligence in order to avoid suspicion.
  • Inverted: Feigning Intelligence.
  • Subverted:
    • Bob isn't fooled for a second by Alice's 'dumb' act.
    • Alice pretends to be naive and unsuspecting, but when she reveals her real self she turns out to be... not so bright.
  • Doubly Subverted:
    • He's not quite prepared for just how smart Alice is, however.
    • She's Book Dumb and bad at forensics, as it turns out. When it comes to social intelligence and puzzling out motives, she's a prodigy.
  • Parodied:
    • Alice's a very poor actor, but Bob is nevertheless completely taken in by her.
    • Alice is a super genius capable of solving derivatives in her head; however, all she has to do to get people to think she's a dunce is say something like "1 + 1 = 11".
  • Zig Zagged:
  • Averted: Alice's disguise does not include altering how intelligent she appears.
  • Enforced: The actor playing Alice is normally cast as a genius and wants to play against type.
  • Lampshaded: "She's not as dumb as he appears to be!"
  • Invoked: "He'll never suspect anything if I act like an idiot."
  • Exploited: Alice gets out of doing favors for people by pretending to be stupid.
  • Defied: "You're not as dumb as you look. Nobody could be as dumb as you look, and still be as successful as you are. I'm on to you."
  • Discussed: "How can someone this dumb be a private investigator?" "Well, she might not be as dumb as she looks..."
  • Conversed: "Alice's such an idiot!" "Yeah? Well, so was Columbo."
  • Played For Laughs: When asked what 1 + 1 is, Alice quotes an obscure law of physics.
  • Played For Drama: Alice lives in a world affected by Tall Poppy Syndrome. If anyone powerful thinks she's too clever, they will get rid of her.
  • Deconstructed: Alice is so good at playing the part of the fool, nobody takes her seriously even after she drops the act.
  • Reconstructed: ...So she continues to act dumb to her advantage. After all, since everyone still doesn't believe her, it gives her the advantage of surprise again.

You're not fooling me! I know you're not stupid, Alice!
http://tvtropes.org/pmwiki/pmwiki.php/PlayingWith/ObfuscatingStupidity