Headcanons!
1: xB loves dinosaurs.
2: Scar had to be told that pet rocks weren't their own species of magical animal and were literally just rocks with googly eyes on them. This was after Joel got him one as a joke birthday present
3: The reason Tango's eyes are red is because he used to be scared of people finding out he was a vexling. So he put in red contacts to stop people seeing they were changing colour. He also started messing with redstone because it stained his hands and face red so no one would see the blue streaks.
4: Welsknight is Hermitcraft's official bs detector. He's spent long enough with the Helsmits to know when someone is lying or deceiving him.
5: Watchers are so used to summoning or using magic to do stuff that most are very very confused by redstone. Particularly redstone farms because why would you spend hours on this moving thing when you can just cheat and summon infinite melons? Grian, Pearl and Keralis (yes Keralis is a Watcher in my headcanon) all shared this mindset when they first joined Hermitcraft
6: Beef can speak villager. No really, he can.
7: Whenever it snows, the hermits all gather. At any point in their fun of building snow castles and snowmen and having fun, someone can get onto the highest visible place, yell 'WAR!' and it turns into an everyone vs everyone snowball war where the last person to surrender gets hot chocolate first.
8: Jevin can use the sun to light fires through himself like a magnifying glass. The first time he did this intentionally, he lit Hypno's hair on fire.
9: Jevin isn't allowed to use this ability anymore
10: Doc knits everyone socks and gloves for Christmas, especially the hermits who have hooves or feet that don't fit normal socks
11: Tango gets cold easily so whenever it's winter you'll see a fluffy blob of Tango shuffling around in the noodles poking them
12: Mumbo always has a spoon on him. Just in case.
13: Joe is the only non-vexling who's ever been allowed into the Vexling only bar (The Summoner). Just because the other vexlings think he's cool.
14: Zedaph is basically a god to the Helsmits. Whenever Xisuma wants something from them he promises that Zed can come over to visit and they immediately accept
15: False gifted Gem a magical wooden sword she can use in any worlds which doesn't have any effect except giving the death message [Player got washed up]
16: Skizz and Impulse have Dad-joke competitions. Grian's won every single one
17: Cub once held a funeral for a rabbit he watched die. Only after the entire 7 hour ceremony was over did he admit that he killed the rabbit himself because it jumped onto his redstone one too many times.
18: Cleo gifted Etho a guess-the-build Etho for Christmas. Etho loved the little guy so much he found/made/bribed hermits into giving him any and all other creations of this little guy. He now has so many he ran out of space in his own base and now hides them around Bdubs's for fun
19: Ren gets zoomies sometimes.
20: Keralis can speak 20 different languages. Only thing is, no one taught him any of them he just could always speak them.