@Crowley  
Jerry: prince blueblood

@Mugen Kagemaru
 
“If the protagonist purchases the Mystery Key from Bratty and Catty, they can enter the house to the right of Napstablook’s. Through a series of diaries, the house is shown to be owned by another ghost known as “Napstablook’s cousin” within the game (though Papyrus states that his headcanon name for him was Happstablook). After meeting Alphys, she designed a body for Mettaton to inhabit.”
 
From the Undertale Wiki.
 
-Lumino

@LuminoZero
 
Nah, that’s the training dummy in the Ruins.

@Mugen Kagemaru
 
Cousins.
 
-Lumino

@Background Pony #C16A
 
Makes sense. Mettaton and Napstablook are brothers in canon.

More wonderful headcanon fulfillment, sweetie as napstablook.

@Mugen Kagemaru
 
This user seconds the suggestion.

This user wishes to see Rarity as Mettaton NEO.

It’s fabulous, daaaaahling!

Napstabelle.

@Crowley
 
How about Double Diamond as 02?

@Celestia’s Servant  
I always thought about that Lil-miss Rarity should be Mettaton Neo.

@LuminoZero
 
Plus that opens a perfect match for his counterpart, chara. What other dragon in the mlp universe shares the same physical appereance (to some degree) to MLP:FIM’s spike?

love it ^^

Aha, yes! I was just doodling this guy!

I’m always gonna see Spike as Frisk.
 
A different race from everyone else. One of them is more powerful than the entire population of the underground. A clean slate, able to be as kind or cruel as the player desires.
 
It fits better than anyone else.
 
-Lumino

Frisk - Apple Bloom/Spike (depending on gender preference)  
Chara - Diamond Tiara  
Toriel - Cadance  
Asgore - Shining Armor  
Asriel/Flowey - Flurry Heart  
Alphys - Twilight (Nerdiness points here)  
Undyne - Rainbow Dash  
Monster Kid - Scootaloo (both idolize Undyne/RD)  
Papyrus - Trixie  
Sans - Pinkie Pie  
Mettaton - Rarity  
Napstablook - Sweetie Belle  
Shyren - Fluttershy  
Royal Guards - Braeburn and literally any other male  
Ice Cream Guy - Carrot Cake  
Muffet - Cup Cake  
Aaron - Bulk Biceps  
Knight Knight - Luna  
Burgerpants - Flash Sentry  
Jerry - Also Flash Sentry  
Bratty and Catty - Lyra and Bon Bon  
Gerson - Granny Smith  
Temmie - Derpy  
Bob - Applejack

Mettapon Ex?
 
Now we need Mettaton Neo, too.

@Masem
 
Soo… not to be that guy but… if Aj is torial, and Big mac is asgore…

Following this artist’s recent Undertale stuff:
 
Twi+Spike as Papyrus + Sans  
Pinkie as Flowey  
RD as Undyne  
Fluttershy as Alphys
 
Then all that’s left, and fits so fittingly, is AJ as Toriel, Big Mac as Asgore, and AB as Asriel

ALL OF MY YES!!!