Natural News (AKA ramblingconspiracybullshit.com, thanks to A Dose of Buckley)
Neocities
Neoseeker
Polygon
The Porn Dude and its subsites
Puyo Nexus
Snafu Comics
Sonichu
TV Tropes
Twitter/X
Multimedia
analog and mascot horror
annoying memes
anything controlled by Retroware/Screenwave Media
Buffy the Vampire Slayer
creepy/gross porn
Cuphead
Cyanide and Happiness
Hello Kitty
Homestuck/Hiveswap
Hot Wheels
IGN
InfoWars
Lego
Miss Kobayashi's Dragon Maid
My Little Pony (yes, really)
Neptunia
One Piece
podcasts
Pop Team Epic/Poputepipikku
Rosario + Vampire
Scott Pilgrim
Sonic the Hedgehog
Steins;Gate
Touhou Project (moreso on the Western Hemisphere, ironically)
Transformers
Yu-Gi-Oh
Diet
advanced.gg
Arby's
Burger King
Cheetos
Chick-fil-A
Coca-Cola
Domino's
Doritos
fruit snacks
Gamer Supps
G-FUEL
Hot Pockets
Jack Daniel's
KFC
McDonald's
Monster Energy
Mountain Dew
Papa John's
Sheetz
Taco Bell
Wendy's
Software
Arch Linux
Discord
Emacs
GitHub
Google Docs
Infinite Craft
Telegram
Conventions
Comic Con
Gencon
MAGFest
MLP Cons
Momocon
PAX
Sonic Expo
Sonic Revolution
TooManyGames
Twitchcon
UK Gaming Expo
VidCon
Youmacon
Miscellaneous
autism
baseball/dad/snapback hats
beanie hats
black dot pupils/"Michael Myers eyes"
blank stares
BPD
completionism
disrespectful behavior
dog collars/"chokers"
Funko Pop figures
Indiegogo
Kickstarter
ko-fi
Neopets
NPD
one dollar/pound stores
OnlyFans
Ownaj dolls
Patreon
plaid clothes
red shirts
road trips
sexual ASMR
skulls
steam trains
subscription boxes
teledildonics
Walmart
Youtooz
Keep in mind that one is not a kidult just because they like children-aimed media; Walt Disney even stated "Adults are kids grown-up, after all." Kidulthood usually combines specific interests with immature actions.