Suggestions by @fehermustang

Josh Hutcherson

as Fluttershy in My Little Pony (Genderswap)

Score: +1

Awkwafina

as Rainbow Dash in My Little Pony: Equestria Girls (Live-Action)

Score: -6

Skai Jackson

as Scootaloo in My Little Pony

Score: +2

Scarlett Johansson

as Princess Luna in My Little Pony

Score: +1

Lizzy Greene

as Sweetie Belle in My Little Pony

Score: +3

Millie Bobby Brown

as Applebloom in My Little Pony

Score: +2

Katherine Langford

as Starlight Glimmer in My Little Pony

Score: +2

Miley Cyrus

as Sunset Shimmer in My Little Pony

Score: +1

Margot Robbie

as Applejack in My Little Pony

Score: +1

Awkwafina

as Rainbow Dash in My Little Pony

Score: +4

Lana Condor

as Rainbow Dash in My Little Pony

Score: -2

Madison Pettis

as Pinkie Pie in My Little Pony

Score: 0

Tyler Posey

as Shining Armor in My Little Pony

Score: 0

Dove Cameron

as Rarity in My Little Pony

Score: +2

Ana de Armas

as Twilight Sparkle in My Little Pony

Score: +1

Drew Barrymore

as Princess Celestia in My Little Pony

Score: +1

Hunter Schafer

as Fluttershy in My Little Pony

Score: -1

Abigail Cowen

as Ginny Weasley in Harry Potter (Perfect Casting)

Score: +1

Taylor Lautner

as Joey Tribani in Friends

Score: +2

Rupert Grint

as Ross Geller in Friends

Score: -6