That's just them being in character. Banana hands is Danny, the energetic, positive and lovable one, so it's in his character to be the only one standing out with disproportionate positivity, even when he's playing roles like Simon Belmont and going on a relentless killing spree as he is in this song. The dude in the back is known as Ninja Brian, who is usually seen actually dressed as a ninja and never says one word or utters any noise ever, but always has a ridiculously stern and scrupulous look in his eyes, like he's always ready at the first sign of trouble to whip out some serious ninja maneuver. Frankly I'm not sure why he was out of costume or why he spoke at all this time, but you're right, you could definitely see traces of him slipping back into his familiar role even though he wasn't in costume. The other singer is Arin, who often plays the role of the angry and passionate one. During Danny's parts, you definitely see Arin looking like he's impatiently waiting for it to end, but that's intentional because he's playing the part of Dracula in this song, as well as Dracula's myriad 'freaky friends.' So when Simon Belmont (played by Danny) is jumping in and disrupting everything, Dracula is visibly showing his frustrated disapproval and wanting Simon to shut up and go away.

i know

Ninja Brian had a prior engagement, so they asked Brian Wecht to stand in.

That One Final Starman XD HE LOOKS PISSED

That One Final Starman I think he's just in character

I wonder if he was nervous

KMP !! Ikr

He loves singing so it only makes sense if he is having fun.

I always want Dan to have fun. He deserves it and it makes game grumps so much better

ThePirateLord Smash would be awesome live

Especially with twrp. It sucks that the only time twrp performed with starbomb was the time when the sound quality was so bad at sxsw. I know they sounded great... just wish the sound quality was better.