The Bravest Warriors use a lot of slang, but, as is the case with Adventure Time, the series is set far into the future and the slang used is nothing like what exists today. As an example, the word "moop" seems to have completely replaced any word that means sadness.
Coach Z fits this trope. He loves to rap (badly), and uses dated slang (which tends to be furthered mangled by his outrageous accent).
In Strong Bad Email #164, looking old, Strong Bad fears he's losing the "youth vote" of "young parsons who eat their yogurt through a tube", and thus calls an "emergency marketing meeting". The Cheat suggests frenetic, MTV-style editing, while Bubs thinks adding a lowercase "i" to the front of words is a good idea. Ultimately he undergoes a "lace-lift" which results in the opposite of the intended effect so that he ends up looking and sounding like his own great-grandmother.
In SBEmail #197, Strong Bad worries he's losing his edge after realizing his recent "shenanigans" have been pretty tame, even by his standards. His ideas of "edgy" involve recklessly destroying his own property by stomping on a casserole while The Cheat saws a hole in the Strongs' living room floor.
Acknowledged yet avoided by the Teen Girl Squad, as their Totally Radical slang is so ridiculous, it can't be anything but fake.
Cheerleader: Okay, my Spanish Galleons!
Their 2010 April Fools gag "Xeriouxly Forxe" is an action-packed revamp of the characters with new "edgy" character designs and Xtreme Kool Letterz. They're "revamped for the nineties"...a decade or two late.
Edgy and angry So zetsy and tangy! There's new demographics When nobody asked for it!
An Important Rap Song is entirely made up of middle-aged voice actor Crack Stuntman trying to deliver a 90's style cartoon PSA about kitchen safety, only to get side-tracked rapping about spring break and the subtle but crucial difference between "fly girlies" and "fresh honeys". The basic concept is outdated, never mind the lyrics.
Strong Bad's Twitter has him posting "TFW" Tweets while being unaware of what the acronym is supposed to mean.
Several of the "Awesome" videos on Newgrounds use this trope for comic effect with characters such as Sonic and Gray Fox. "Yo yo yo B-boy Snake-Dawg-G..."
Houshou Marine and Mori Calliope of hololive are affectionately described by their fans as boomers:
Marine's tendency to act like a woman much younger than herself (she claims to be 17, both before and after celebrating a birthday ("Seventeen second season!"), but has accidentally revealed herself to be in her late twentiesnote Not that she really tries to conceal her age, outside of comedic circumstances anyway. In more serious talking segments, she openly shares her experiences from when she was working in a black company.) results in both fans and other members pointing out that she should act her age, since she inevitably embarrasses herself when the comparatively younger members are able to either outperform her physically or point out how dated her cultural references are. Her less-than-perfect grasp on the English language is further compounded by the fact that when she decided to ask someone to teach her contemporary English slang, the one she asked was fellow boomer Mori Calliope (see below). Case in point, her profile description on Reddit:
HoushouMarineLEGIT: Based, super-lit, dope, beautiful young girl (NOT BOOMER), I don't have a pirate ship, but I have the pirate spirit super lit!! ( lmao)
Calliope tends to use dated slang in a very stilted manner (such as referring to herself as "your boy"[sic]), as she's both inhuman and ageless, so her communication skills with modern humanity leave something to be desired. It's not helped by the fact that, even when she does use modern slang, she's old enough that the meaning of some of it has changed, and she didn't know until her fans pointed it out note Most noteworthy would be her use of the word "yeet". While it is now primarily used to refer to throwing things, it also used to be used as an expression of approval, which is the usage Calli was familiar with, and most of her audience was not.
as their Totally Radical slang is so ridiculous, it can't be anything but fake.Cheerleader: Okay, my Spanish Galleons!