The Leonov crew's triangular mission patches show both the Soviet and U.S. flags, but the U.S. flag is upside-down: the stripes are on top and the stars are on the bottom. Flying a flag upside-down is only supposed to be used to signal a dire emergency... but the reason there are Americans on this mission is precisely because needing to rescue Discovery before it crashes into Io is a dire emergency. — SuddenFrost
Wouldn't the existence of two suns mess with various animal/plant life cycles that are dependent on a day/night cycle?
It would, and it was explicitly mentioned by Arthur C. Clarke in his novel.
When Earth is between the Sun and Jupiter, it is still about 900-1000 times further from Jupiter than Europa is. Assuming Jupiter looks from Europa like the Sun from Earth, its magnitude from Earth would be -12m. That's about 10000 times brighter than Sirius - and about as bright as a half moon. Meaning that the night sky would look like in a moonlit night, except with a very brilliant dot. Farthest from Earth, Jupiter would still be almost half as bright at -11m, and still a very bright dot on the day sky.
So, in other words, the night sky as we know it would still exist, just with at least one light source being equivalent to a half-moon being present at all times? Notwithstanding the effects on sea turtles, migratory animals, etc., that doesn't sound quite drastic enough to warrant lovers' being ticked off as Clarke proposed.