Did some stats on part of my watchlist. According to the stats I watch 28 Season 1 characters, 17 from Season 2, 2 from Season 3, 8 from Season 4, 20 from Season 5, 21 from Season 6, 24 from Season 7, 14 from Season 8, 3 from Season 9, 1 from Rainbow Roadtrip, 2 from Ponyville Mysteries, 7 from IDW, 10 from G1, and 14 from G3. Correct me if I’m wrong.
Season 1:
apple bloom
apple fritter
archer (character)
aura (character)
blueberry cloud
blueberry punch
cheerilee
cotton cloudy
diamond tiara
dinky hooves
lemon daze
lily dache
noi
peachy pie
piña colada
rainbowshine
royal blue
ruby pinch
scootaloo
silver spoon
snails
snips
sun glimmer
sunny daze
sweetie belle
tootsie flute
tornado bolt
twist
(I counted Limestone and Marble as Season 5 characters as they had no character beyond Pinkie’s sisters until then and the backstory was retconned in S4)
Season 2:
allie way
alula
bloo
blossomforth
button mash
cloudchaser
featherweight
flitter
ginger snap
mjölna
nursery rhyme
nurse sweetheart
pipsqueak
rumble
silver spanner
silverspeed
thunderlane
Season 3:
babs seed
opal bloom
Season 4:
air way
brown sugar
lilac sky
maud pie
peach fuzz
spring step
train tracks (character)
zippoorwhill
Season 5:
bubblegum brush
carrot crunch
cotton puff
cotton sky
lily longsocks
limestone pie
marble pie
moondancer
moonlight raven
morning roast
night glider
rainberry
rainbow stars
starlight glimmer
sugar belle
sugar stix
sunburst
sunshine smiles
whoa nelly
winter lotus
Season 6:
angel wings
burning passion
carrot bun
crackle pop
eye black
gusty sprite
heart pacer
hyacinth dawn
minty bubblegum
pacific glow
perky prep
petunia paleo
plaid stripes
pretzel twist
princess flurry heart
strawberry parchment
sweet biscuit
tender taps
thunderstruck
violet spark
windy streak
Season 7:
chipcutter
coconut cream
dust brush
gentiana
glitter spritz
indian summer
inky rose
jasmine leaf
kettle corn
lilac ice
lily lace
miss hackney
mocha berry
pear butter
raspberry cream
raspberry vinaigrette
skeedaddle
somnambula
star tracker
strawberry sunrise
teal shores
toola roola
tulip swirl
windy whistles
Season 8:
appointed rounds
autumn blaze
bifröst
coral currents
cozy glow
high tide (g4)
lemon crumble
minty mocha
peppermint goldylinks
rainy day
raspberry latte
sandbar
strawberry scoop
valley glamour
Season 9:
bellflower blurb
lemon honey
spur
Rainbow Roadtrip:
kerfuffle
IDW:
cherry blossom (idw)
cirrus cloud
cocoa axe
gilded lily
nimbus dash
sun cross
thestra
Books:
ambermoon
lilymoon
G1:
galaxy (g1)
gusty
minty (g1)
paradise
shady
snuzzle
sundance
sweet stuff
wind whistler
G3:
azalea bloom
cheerilee (g3)
fluffaluff
mayor flitter flutter
midnight dream
minty
razzaroo
scootaloo (g3)
starsong
sweetie belle (g3)
thistle whistle
tiddlywink
tra-la-la
zipzee
Interestingly, Seasons 3 and 9 have the same order both alphabetically and by the characters’ debut episode.