Alien skies: how largest moons are visible from their parent planet's surface. Jupiter's Io, our Moon and Neptune's Triton are largest. So, alien skies are no so shiny like in movies. No giant moons covering half of the sky, sadly. At least in our Solar system.
Picture made by changing ParentBody of largest moons to Earth, then adjusting orbit Inclination / AscendingNode / MeanAnomaly in the editor.
Edit: well, skies on some alien
moons are more spectacular than on planets. For example, from Europa, Io and Ganymede sometimes looks twice larger than the Moon from Earth. Not saying about parent planets themselves...
Edit2: some inner asteroid-like moons on gas giants sometimes could look as large as Ganymede.