D4C, or Dirty Deeds Done Dirt Cheap, is a Stand in JoJo's Bizarre Adventure: Steel Ball Run, that allows Funny Valentine to traverse parallel universes. It enables him to pull alternate versions of himself and others into his world, and also to transfer his consciousness to a different version of himself in another universe, effectively granting him a form of pseudo-immortality. This ability is key to his plan to collect the Saint's Corpse pieces and conquer America. 

Here's a more detailed explanation:

Dimensional Travel:

D4C's primary ability is to create a portal to a parallel universe by passing between two objects. Valentine can then travel through this portal and bring objects or people from the parallel universe into his own. 

Alternate Selves:

Valentine can bring alternate versions of himself from other universes into his own. This is crucial for his survival, as he can transfer his consciousness and Stand to a different version of himself if his current body is injured or killed. 

Love Train:

When Valentine gains possession of the Saint's Corpse, D4C gains the additional ability of "Love Train". This ability creates a pocket dimension, a gap in space, that Valentine can enter, making him virtually invincible. Attacks and misfortune are redirected away from him and toward another location or person. 

Interdimensional Collisions:

While Valentine can move freely between dimensions, other beings brought from parallel universes will be obliterated if they come into contact with their alternate selves. Valentine is the only exception to this rule, allowing him to work with his alternate selves without consequence. 

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