I remember when JitteryTheDragon made a comic about Undertale and MLP (which the comic can be found here: knowyourmeme.com/photos/109435… since his deviantart account got deactivated).
 
However frisk and spike are basicly related because that they are kids but different species.  
also The DifferentTopic AU Owner (which known as GonzaloGamer128NEW) planned Spike to be in his game but he decided to replace him with Casper instead. I don’t know why Casper was chosen even though Casper is a friendly ghost and to be fair Casper should take the role of Napstablook instead of Asriel.
 
Anyways, I planned to do the mugshots and a battle Sprite however I couldn’t do them in Paint.net because the lack of coloring… Also I was gonna use vector sprites for the mugshots and the battle Sprite… so yeah…
 
Also about the Frisk hugging Spike sprites that I had an idea for something in treating that it sorta inspired by DifferentTopic AU(which that the owner of the AU made him a role of Asriel, But now Spike is replace by Casper.) However I made this just for fun… and about the handshaking part is when Frisk meets spike for the very first time (Yeah it’s a referance to sans’s handshake) however there is no whoop i.e. cushion on spike’s hand.
 
However I couldn’t add the wings because Undertale was made in 2015 and Spike got wings in 2018 during season 8. So yeah…  
I don’t know if there is gonna be a MLP G5 because every generation last at least 10 years. so yeah…
 
Also what does dragon should look like in undertale? I’m thinking that they look like gem hearts because Human souls are shaped like hearts and Monster souls are white upside-down hearts.
 

 
Spike the dragon belongs to Hasbro  
Undertale belongs to tobyfox
 
UPDATE 4/7/2019: