These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Acceptable Targets: In the Civilization video, Brent illustrates the "spread your equally valid religions" line with props from various faiths. Three of these shots are basically respectful; the fourth, for Christianity, features Pedobear in a pope hat. (For extra points, the Islam shot makes fun of Fox News.)
Likewise, "Baby Mario & Papa Yoshi" shows Yoshi planning to cook and eat Baby Mario when he first saw him, but he slowly changed his mind and decided to raise the baby himself.
Crosses the Line Twice: Tetris With Lyrics which goes on in great length about how girls are inherently addicted to Tetris. The particular moment of the second line crossing is when he uses the tune to hypnotize his girl into forgetting he's a dick.
His performance of the oddly upbeat Game Over music from Mega Man 3 with lyrics. It would be annoying if the game was just making fun of you for dying, but seeing Floss dressed as the cartridge in a top hat while cheerfully singing about how worthless you are, how everybody hates you, and that your mom should've "drowned your ass in boiling water"? Hysterical.
Fridge Logic: In Phoenix Wright with lyrics, clips from Apollo Justice: Ace Attorney despite being the fourth canon game in the main series (As opposed to being a spin-off) and Phoenix being a major character in said game, are surprisingly absent. (and to a lesser extent Miles Edgeworth Investigations, which actually is a spin-off). Well, the song is called "Phoenix Wright with Lyrics" so the fact that all the games shown in the video have "Phoenix Wright" in their respective titles, makes perfect sense. (After all this is "Phoenix Wright with lyrics" not "Apollo Justice with lyrics")
Nightmare Fuel: "Kirby With Lyrics" has a disturbing take on the title character, similar to There Will Be Brawl. It depicts Kirby as a monster whose only purpose seems to be devouring everything and everyone. Of course, it is a part of Flosstober.
Painful Rhyme: his cover of the Zelda main theme begins with one.
"Do you recognize this melody? Well, duh..."
"But why? 'cause it's The Motherfucking Legend Of Zelda!"
And in his Civilization cover:
You can change the future a lot, see? You can even make Jewish Nazis!
Tear Jerker: "The 2-2 Blues"; a Randy Newman-esque arrangement of the Underwater theme from the first Super Mario Bros. game, all about how, no matter how difficult the quest to save her may be, Mario will always keep swimming towards Peach.
Also, the video "Brent & Brett: Game Drunks" (essentially, the Floss Man and Brent Vanderbrook of Captain S fame play a drinking version of video games - each failure or in-game death means a swig of beer, with a shot of harder - and apparently disgusting-tasting - alcohol for losing a round.) After Floss takes one more shot for losing in Call of Duty, it goes to a black screen saying that they both died of alcohol poisoning. And sad music as well.