A more subtle one in the Point/Counterpoint PSA on tattoos. Church (Burnie) argues against getting tattoos while Grif (Geoff) argues for tattoos. In real life Burnie has no tattoos while Geoff is covered with them.
In Season 11, Grif's teleport cubes get compared to Pokeballs from Pokémon. Grif's hostile response mirrors Geoff's attitude towards the series whenever it's brought up.
Elijah Wood as the evil, creepy Sigma. Mind you, this isn't the first time he's taken up the role of a villain.
North Dakota is a fairly serious guy. His VA is a professional comedian.
Miles Luna, who played JauneArc in RWBY, plays the very much badass Felix. Moreso in Season 12, when he turns out to be one of the bad guys.
Promoted Fanboy: Gavin Free was originally just a fan of series from the beginning, but took over from Burnie Burns as director for Relocation (the miniseries between Seasons 6 & 7), as well as for all of Season 7 itself.
Hilarious Outtakes: There's an audio clip of "Gavino" reading The Director's letter from the Reconstruction Trailer, before Burnie interrupts, clarifying that he didn't want him to be "The Director for the season" he wanted him to "direct the season".
Gavin: "Oh... Oh. I get it. My- So I should just-"
Burnie: "Get the fuck out of the booth, okay?"
In another direction, the RvB franchise getting nods in the various Halo titles, the biggest being the 'Password Forgetting Marine'Easter Egg in Halo 3 which features RvB voice actors, though they are not officially their characters, but are pretty clear who they are. The voices and dialog depend on the difficulty level:
Normal: Tucker and Doc.
Heroic: Simmons and Grif.
Legendary: Church and Caboose.
What Could Have Been: Doing the Animated Adaptation was an ambitious idea, but the crew just didn't have the money and time for it. They also didn't like the fact that someone else had to do the animation, so they couldn't do it in-house.