I have a theory about D&D Bugbears (which you can feel free to incorporate into your own games):
We are told by The MOM (Monsters of the Multiverse) that Bugbears’ fey ancestry grants them two fey gifts. The first gift is, of course, a resilience against charms. The second gift is one of stealth; A magical ability to stay hidden “just out of sight” by hiding “…in spaces seemingly too small for them.”
HOWEVER, we are still given no explanation as to how Bugbears’ arms can reach as ridiculously far as 10 ft., other than “idk arms kinda long I guess lol”. I’m sure this answer is fine for some people, but not for me—especially since I just thought of an alternative that I’m MUCH more excited about:
The REAL reason Bugbears can reach 10 ft. with their arms and easily fit into spaces that should be a Size too small for them, is that their second fey gift is not one of stealth, but one of space manipulation; They have an innate magical ability to alter how space works, but only for themself.
- Can’t hit enemy cuz they’re a little too far away? Alter the space around your arm so you hit them anyway.
- Can’t fit in that drawer? Alter how your whole body takes up space so you can squish in there.
- Trying to hide behind a tree but you’re too big? Once again, alter the space your whole body takes up, so the tree fully covers you!
It’s possible that this ability is very limited due to Bugbears’ far removal from their fey roots…
But it may also be that this distance has not made Bugbears any less powerful—they’ve simply forgotten this ability of theirs, and thus can only use it unconsciously via belief of how things “should” work for them. They think their arms are long enough to reach 10 ft., so they are. They think they can fit in that drawer or be entirely covered by that little tree, so they can. Maybe that’s also why they can lift the same amount of weight as a Large creature—they think they can.
TLDR: Bugbears have space-warping abilities, which is why they can reach so far. Their stealthiness results from them using their space-warping to hide in too-small spaces. Also they might be similar to Orks from WH40k.