Extendable Arms

Take a cartoon, preferably an older one, and find a pair who always end up in fights. Tom and Jerry, Dick Dastardly and Muttley from Wacky Races or virtually anyone from Looney Tunes. Somehow, one character always has a fist which can stretch across an entire country. Or a continent. Or a universe.

For decades, super stretchy limbs have been popular superhuman abilities. Whether they're used for a cartoony Visual Gag or are part of a Rubber Man's powerset, they're practical, funny-looking, and even badass. Being able to hit a dangerous person from a safe spot, or a moving target you can't otherwise reach is a boon in a fight, and being able to grab something that is separated from you by a bunch of lethal traps can also take a lot of pressure off you. And of course, it can make something as mundane as grabbing a phone or a slice of pizza without moving just plain cool.

Keep in mind that this trope isn't just relegated to arms: extendable legs, necks, and... well, other body parts can invoke this trope, arms are merely the limb that instantly comes to mind. Not to be confused with Rubber Man, but there's definitely overlap since stretchy arms come with the territory.

Fan Works

 * This turns out to be an ability Touji's Evangelion possesses in the Neon Genesis Evangelion fanfic Neon Metathesis Evangelion by "Octo8". Unfortunately for Touji, it's incredibly painful to use.

Film

 * In an exceedingly rare live-action example, in the Chinese kung-fu movie Master of the Flying Guillotine, an Indian fighter enters a tournament with the power to extend his arms to an absurd length.
 * Michael Jordan uses this to make a slam dunk in Space Jam taking full advantage of the Toon Physics of the movie.
 * Freddy briefly extends both his arms to scare his victim in the first A Nightmare on Elm Street film.

Video Games

 * This is one of Dhalsim's trademark abilities in the Street Fighter series—through the power of Hollywood Yoga, he can strike from the other side of the screen.
 * In Sonic Unleashed, Sonic has arms that extend in his werehog form.

Western Animation

 * In The Thief and the Cobbler, the Witch uses this to pull down a hesitant character (who s much bigger than she is) for examination.
 * Tom and Jerry demonstrates this several times, often when Tom tries to reach for Jerry inside one of the walls.
 * Often used in conjunction with strategically placed mousetraps.
 * Used by Dick Dastardly whenever Muttley starts laughing at him, outside the range of a typical human being.
 * Pinkie Pie from My Little Pony Friendship Is Magic has these, but she uses them to pull her friends in for a group hug.
 * On Family Guy, Lois's father once punched Peter through an email.
 * Though it doesn't involve combat, the mid-1980s Scooby Doo series had Daphne restrain a fleeing Shaggy by extending her arms from off screen.
 * Spongebob Squarepants uses this trope often. One episode even had Squidward's limbs used in this manner to keep Spongebob's rotting house from collapsing. (against his will of course)
 * Spinel from the Steven Universe franchise has these, being a rubberhose-like character.
 * The robots in Rolie Polie Olie can stretch their metallic limbs at will.