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 universe. This is a type of Toon Physics, and is often used with revenge.

Not to be confused with Rubber Man

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.