Not to mention Gibraltar - everyone's overlooked this tiny rock, but Gibraltar is entirely dependent on EU freedom of movement and voted very heavily remain. It's not a coincidence that there was a Gibraltar diplomatic mission to the SNP conference, although I'm not entirely clear what they wanted other than solidarity against Brexit.

Maybe Spain would let in Scotland and claim Gibraltar as their own?

Spain is already claiming Gibraltar as its own.

Is just that not the UK neither the people in Gibraltar want that. But yes, Gibraltar could face some problems when the UK leave the UE.

Why would they claim it as their own if the population is not Spanish?

Short version: look at a map.

Long version: https://en.wikipedia.org/wiki/Disputed_status_of_Gibraltar

If the population does not want to be part of the country, one cannot just annex the territory in the modern times.

Correct. That said, if the UK leaves the EU, and freedom of movement goes away, the opinions of Gibraltar's residents may change fairly rapidly.

You're assuming the EU will want it.

Germans are going to face a large hike in their contributions to the EU in the next few years as the UK leaves, as the EU appears to be utterly incapable of actually spending less (despite now having diminished responsibility). That's just not in its nature.

So then Scotland comes along. The best available data says it's an economic basket case significantly worse than Greece. The UK subsidises it to a great extent for historical and cultural reasons that don't apply to Germany. Meanwhile, 40% of Scotland voted out of the EU as well.

If you're German and already questioning whether you should be subsidising lots of low productivity high debt Mediterranean countries, does the thought of waiving the entry requirements and then paying even more taxes to subsidise a new Greece appeal to you?

Don't know why this has been downvoted. It's on topic and not even a particularly controversial line of argument. I'd hate to think downvotes were happening due to prejudice, but it does seem that the left wing wants to suppress differing opinion these days.