All Germans Are Nazis: In his "Mega Man Boss Interviews" video, Top Man says he wanted to be named Dreidel Man but the German Dr. Wily wouldn't let him. Also, in the "Civilization with Lyrics" video he thinks making Judaism the official religion of Germany is sufficient for creating "Jewish Nazis."
A Winner Is You: "Classic Ending Credits with Lyrics" is an extended musical rant about this trope.
Broken Base: The central subject of "What if Super Mario Land Had Lyrics?". On one side, you have collaborator Dave Bulmer who praises the game for setting the trend of handheld platformers and handheld gaming in general, while on the other, you have Brent arguing that the game simply hasn't aged well.
Butt Monkey: In most of the pages in the Brentalfloss comic.
Call Back: "Super Mario Land With Lyrics" has Dave calling Brent a "son of a taint", which is a call back to Brent's much earlier "Mega Man 2 With Lyrics", and Dave asking Brent "Key change, mofo?", a call back to "Final Fantasy With Lyrics".
The "Mega Man 2 Title With Lyrics" describes Mega Man as "blue and cyan", which was also a line in "Mega Man 3 With Lyrics"
Early Installment Weirdness: His earlier videos tend to use more official art and screenshots rather than Brentalfloss himself dressing and acting up as characters.
Farts on Fire: The "Baby Mario & Papa Yoshi" video has Baby Mario give Yoshi a flaming fart to the face after touching a Fire Flower.
Freeze-Frame Bonus: Several. For one example, there's a part in the "Kirby with Lyrics" video where a crowd is running away from Kirby in fear. Most of them are cosplayers, and pausing the video allows you to see a lot of characters are being cosplayed (Luffy, Law, Ash, Misty, Cloud...).
Just for Pun: The name of his third "With Lyrics" album, Flossophy.
Konami Code: This forms the chorus of the "Contra with Lyrics" song.
Laser-Guided Karma: As shown in this video, Brental Floss was holding a small online auction where he was selling his stuff and would use the money to help him and his girlfriend move into a better apartment. One of the things he offered to sell was a 30 minute phone call between him and the buyer and he set the starting bid at 99 cents. At the end of the day, the winning bid was over $800, but Brental Floss wasn't paid for days and after finally getting a response from the bidder, said bidder bluntly stated he would refuse to pay him. Brental Floss looked up the bidder's profile and other info and discovered that the bidder was a 15 year old Brony with a Facebook account. After getting the kid's phone number, Brent's girlfriend called the troll and pretended to be a representative claiming that the kid won a contest and had won a bunch of prizes related to My Little Pony. After getting the troll's hopes up, the phone was passed over to Brent who then gleefully called the troll out. Lesson learned? Don't troll a troll.
Lyrical Dissonance: One of his songs takes the upbeat, energetic tune from the Mega Man 3 game over screen... and sets it to a "The Reason You Suck" Speech directed at the player, with lines like "You're a sack of putrid shit! Dig a hole! Jump in it!". Lampshaded by the introduction: "Sure, the "game over" music from Mega Man 3sounds happy. But did you ever get the feeling that the game was just being a dick?"
Also in "The BioShock Song", a carefree jazz number about the many horrifying things that can happen to you in Rapture.
Dr. Mario: Take it, Floss! (Piano solo by a handsome bald man)
Something Completely Different: Occasionally, instead of putting lyrics to video game music, he'll put new lyrics about video games to songs that already have lyrics. For example, Super Mario World to the tune of What A Wonderful World.
He also has "Without Lyrics" videos, which is him playing the original music.
You're not quite as good as everyone else who plays it.
Don't continue, just give in,
You silly boob, ya fuckin' noob,
Just turn off the power and cry yourself to sleep, you pussy."
Take That: Several, but his entry about Rayman (or, more precisely, Rayman Legends) in his "Game Over Tinies" song stands out - his stance about the game's delay to a more unfortunate release date is as straightforward as it gets.
A lot of his comics that had to do with the Wii U irked Nintendo fans, as the punchlines were nothing more than "The Wii U Sucks" over and over again. He referenced the backlash in his "Farewell song" for the comic.
Truck Driver's Gear Change: Used and lampshaded in Final Fantasy with Lyrics, Civilization with Lyrics, and This Is the Album You've Been Waiting For (his promo song for his "Bits of Me" album. "Key change, mofo!"