Trickster Twins

Woe the fictional parents of the Trickster Twins, a set of siblings always up to no good, much to their sadistic delight. Oftentimes, their antics are strictly for comic relief, but other times, their tricks can be far more sinister. A set of Trickster Twins usually have the tendency to get themselves into trouble and often have to find a way through a series of convoluted plans to escape the situation. Sometimes, they have the tendency to Twin Switch. The traits most common to a set of Trickster Twins is that they're pranksters or entertainers.

Trickster Twins also have the good-natured compulsion to pick on or tease the rest of the cast. If they target a single character out of the entire cast, that victim is usually the Butt Monkey. May overlap with Think Twins depending on their cunning.

Anime and Manga

 * Kaoru & Hikaru in Ouran High School Host Club. (They even appear as Cheshire Cats during a Homage to Alice In Wondeland.)
 * Shion & Mion in Higurashi no Naku Koro ni. Sometimes, it's funny. Other times, it's not funny at all.
 * Fuuka & Fumika Narutaki in Mahou Sensei Negima. Notably, Fumika is more reserved and often states that Fuuka's pranks aren't such a good idea, but she always gets dragged along and always gets into it anyways.

Comic Books

 * Pride High has Smash and Crash. They finish each others' sentences, can trade places with one another in an instant (which they slyly use while wrestling) and remain the most devious of the the prime group of antagonists.

Literature

 * The Tibble Twins from Arthur
 * Harry Potter: Fred and George Weasley
 * Bonnie and Beanie, the little teleporters from Theodore Sturgeon's More Than Human.
 * The eponymous characters from Edgar and Ellen fit this trope to a T.
 * The Otis twins, AKA "Stars and Stripes" from The Canterville Ghost.
 * Hugal and Monan from the Dungeons & Dragons Eberron novel The City of Towers thrive on twisting mind screws.
 * The Stoll brothers from the Hermes cabin in Percy Jackson and The Olympians.
 * "Trouble Twins" Florida and Dallas from Ruby Holler, although it's justified in that they're mistreated by the owners of the orphanage they live in and strike back in the only way they can; Dallas is a Nice Guy and Florida is a Jerk with a Heart of Gold.
 * Bertie's cousins Eustace and Claude in Jeeves and Wooster.
 * Who can forget all the crazy antics of the Lannister twins? Incest, pushing kids out windows, regicide...

Live Action TV

 * Zack and Cody from The Suite Life of Zack and Cody

Newspaper Comics

 * Hans and Fritz, the Katzenjammer Kids
 * Of course, the Katzenjammer Kids are derived from the earlier Max und Moritz (1865) by the German Wilhelm Busch.

Video Games

 * Dee and Dum from Heart no Kuni no Alice. Their tricks range from the innocent to the... not so much.
 * Pokémon Black and White: Tornadus and Thundurus, both of which have the Prankster ability.

Web Comics

 * Eerie Cuties got Cessily's younger sisters, Neige and Sorbet. As early-teen fairies, they really embrace the prankster side of life. When the new demon kid ended up in their house, they quickly adapted — Tia gets to boost her ego by calling them her "minions", while they get to explore new and fascinating avenues of mischief Tia's magical power opens for them, like crashing a party via teleport circle.

Western Animation

 * Edgar and Ellen, as noted above.
 * Phil and Lil from Rugrats
 * Jim and Tim, the Tweebs, from Kim Possible, also doubling as Think Twins.
 * Zim and Zam, Yzma's nephews from The Emperors New School (voiced by Dylan and Cole Sprouse, who play Zack and Cody).
 * The eponymous "Twins" on the Adult Swim show Superjail.
 * Wilykit and Wilykat from Thundercats and ThunderCats (2011)