I know the original game did this too, but large units (2x2 tiles) sometimes spawn inside small rooms in OpenXCOM. Sometimes it's not a problem, sometimes it's rather annoying. I'm attaching two saves:
1. Hallucinoid blocked the lift for several turns before it finally moved away and I could kill it.
2. Triscene appeared in a ship cabin. This one was super annoying, because I spent about half an hour checking all the cabins.
It would be nice if this was fixed... eventually.