For the sake of the easter egg, this answer should be accepted (even if not exactly correct :o )
I think that would be used if the snake had taken up a permenant residence in the shoe, or was otherwise irremovable
If so, extremely rarely. There are basically only two kinds of snakes here, one is the 'grass snake' which is totally harmless and the other one is a viper or adder which is venomous but very rarely lethal. They're both pretty shy and don't try to get into people's homes. (We also don't really have any venomous spiders or other insects – I think there's only one which is extremely rare and only mildly venomous too – so the wildlife here isn't very dangerous, so long as you don't crash you car into a moose or try to play with bear cubs. Or camp out in a swamp without a mosquito net during the mosquito season… )
In an earlier question, "There is a snake in my shoe" translated to "Det är en orm i skon". So how do you translate to English this sentence? "There is a snake in the shoe" or "There is a snake in my shoe"? Perhaps Swedes would immediately think "in my shoe" upon reading or hearing that sentence?
Yes, I wrote about it in this thread: https://www.duolingo.com/comment/6014446
'my shoe' is an accepted answer here too but I think in this case we'd be more likely to say Jag har en orm i skon 'I have a snake in my shoe' if it were really about one's own shoe. (this is our only sentence about a snake in a shoe :))
If you were talking to someone, could this sentence also be interpreted as "there is a snake in your shoe"?
I suspect then a Swede would be more likely to phrase it 'du har en orm i skon!'
Are there "poisonus plants" in Sweden, i.e. plants that produce urushiol like Poison Ivy? I have to say it's probably the worst thing about going into in the wilderness in America
We do have plants that could kill you if you ingest them, like most places do, although they're rare and why are you eating plants anyway? :p
Luckily, there's no poison ivy. You may run into a lot of stinging nettles, though.
The name is misleading. They're not just poisonous to eat. The oil leaves painful blisters if you touch it http://www.mayoclinic.org/diseases-conditions/poison-ivy/basics/definition/con-20025866
The plants that are most dangerous to touch here are probably björnloka Heracleum sphondylium ("commonly known as hogweed, common hogweed or cow parsnip") and jätteloka, Heracleum mantegazzianum (commonly known as giant hogweed, cartwheel-flower, giant cow parsnip, hogsbane or giant cow parsley). They burn your skin, especially if your skin is also exposed to sun afterwards. They can cause pain for weeks, discoloring of the skin, and scarring.
Our Environmental Protection Agency Naturvårdsverket actually recommends making the latter species extinct in Sweden in view of its being an invasive species as well as poisonous, and people are trying to reduce the number of the first species too.