Scooby-Doo Effect 

The act of the villain telling the audience (be it in a TV show, novel or play) the crafty ins-and-outs of his or her plans, more often than not after they have been caught out or caught in the act.
More often than not this relates to the exact moment that the rest of the characters learn about what exactly has been going on.

"So that was my plan: to steal the plans for the new Multi-Storey car park from the Town Hall so it could never ever be built.
And I would've gotten away with it too if it weren't for you meddling kids!"

The Scooby-Doo Effect in action.

Scooby-Doo Effect by Rankles February 24, 2009

Scooby Doo Effect 

When you can tell which objects in an animated film or video game are supposed to be picked up or manipulated by a character because they "pop out" from the rest of the scene. The effect is achieved by: (a.) making the stand-out object brighter,

(b.) making it a different shade of color than similar surrounding objects, or (c.) in the case of video games, making the object shiny or pulsing with light (intentional scooby doo effect).

The original effect was an unintended side-effect of cel animation. Animators would use the same slides over and over for static backgrounds and place the animation slides over them (e.g. the same picture of a room will be used for several hundred frames because the room never moves, but the characters have to be redrawn each frame with new slides).

The inconsistency of color and brightness between the new painted slides and the original background slide causes the animated object to stand out from the background. The Scooby Doo cartoon was a particularly noteworthy example of this effect in practice.

(playing a video game) "There's some major scooby doo effect on that door. I'm pretty sure you can open it."

Scooby Doo Effect by Boondiggle August 14, 2020

The Scooby Doo Effect 

When someone undeservingly stumbles upon success, through sheer luck and usually minimal skill of their own, similar to that of the cartoon character Scooby Doo who would often catch the villain by literally stumbling upon them, usually after he had fallen over or been involved in some sort of zany accident.

Person 1: Hey, how'd you go in that exam?
Person 2: Dude I got like 95%
Person 1: How? I got like 65% and you told me you didn't even study
Person 2: It's the Scooby Doo Effect man.

The Scooby Doo Effect by Opium Daydream July 21, 2010