It's really strange, whenever he's doing a Co-op stream with another Streamer he basically turns into that person for a while.
It doesn't really make sense to me because Joel doesn't seem that lonely considering how he's hanging out with some of his mods in Sweden and regularly has that American guy over at his place.
It's hard not to adapt to the sense of humor of your audience, even if that "audience" is just a friend who jokes differently than you. This is pretty easy to see with Vinny, too, in the very rare co-op streams he does. Any stream between him and Imakuni is a perfect example, but especially their Animal Crossing: New Leaf stream - Imakuni has such an infectious, bubbly energy that it even rubs off on Vinny, and he is audibly in a much better mood than is normal for his streams.
I think the same can be said for Joel, and it probably doesn't hurt that he seems to genuinely like Jerma and Simpleflips, too. It makes it a lot easier for him to get more in their headspace and vibe better with their sense of humor. There's a reason why their co-op streams tend to be some of the most viewed in spite of their rarity, and I definitely think that's a big part of it.
I think he just genuinely respects and tries to emulate the other streamers he streams with. Like, he's not shy about sucking Simple and Jerma's dicks. It's adorable in a way, and I can definitely relate to wanting to emulate people you respect.
That or Joel is a body snatcher and is trying to replicate them. Which, based on the stickiness of some of his earlier streams, wouldn't surprise me.
Joel's early streams definitely play out like an alternate universe where Young Vinny got really into Metalocalypse and cigarettes, and it's undeniable that he had some kind of platonic hard-on for Vinny for a few years there. Even so, I do have to appreciate his candidness in showing off his friends to the audience; it doesn't feel like a plug to me, so much as a "guys guys look at my new friend omg isn't he cool!!! I love my new buddy!!"
The fact that Joel is, to my knowledge, not affiliated with any larger companies (like Vinny apparently is) reasserts to me that he just streams with the people he likes and doesn't really bother to hide his affection for them. It's very genuine, and yes, very adorable.