Most of Jupiter's moons are less than 5 km across.
Of Jupiter's moons discovered so far, 55 of them are less than 5 km in diameter, or about 15.7 km in circumference. Assuming 15 minutes per km, and of course ignoring the effects of gravity (and the fact that there wouldn't be any air) a person could walk around one of these moons in about 235.5 minutes— just under 4 hours.
Jupiter is twice as massive as all of the other planets in the solar system, combined.
With a mass of 1.899 × 1027, Jupiter has the mass of about 318 planet Earths, or twice the mass of all of the other planets, combined.
Over 1,000 Earths could fit inside Jupiter.
Jupiter is, by far, the largest planet in the solar system. It has a diameter 11 times larger than the Earth, and could fit just about 1,317 Earths inside of it, by volume. Saturn, the runner up, has about half this volume.
You'd weigh about 253% as much on Jupiter as you do on Earth.
Because Jupiter is so massive, it has a much stronger gravitational pull than Earth. You'd weigh just over 2.5 times your Earth weight on Jupiter.