Since Blue and the others (except Steve) were 2d in the show, it would make sense to make everyone here except Twilight 2d as well.
 
Cast:  
Twilight as Steve (Both are the main protagonists)  
Spike as Blue (Both are dogs)  
Sweetie as Tickety (Similar color schemes, and their names rhyme)  
Derpy as Mailbox (Both deliver mail)  
Mr. and Mrs. Cake as Mr. Salt and Mrs. Pepper (Both are chefs in a kitchen, even though they don’t have a French accent)
 
Vectors by SketchMCreations, thatguy1945, illuminatiums, Bronyboy, and Brony-Works.