It's about 1,000 times as heavy as a liter of Water
In other words, 999 kilograms is 998.9720 times the weight of a liter of Water, and the weight of a liter of Water is 0.001001029 times that amount.(fresh; 4° C / 39.2° F; maximum density)
Contrary to popular belief, 1 liter (0.0.264172052358148 gal) of water at 4° C / 39.2° F (its point of maximum density) weighs 1.000028 kg rather than 1 kg exactly. The total volume of water on the planet Earth is about 13,590,000,000,000,000,000 (13.59 quntillion) L (3,590,000,000,000,000,000 gallons).
It's about 750 times as heavy as a Human Brain
In other words, the weight of a Human Brain is 0.00135 times 999 kilograms.(adult)
The average weight of an adult human brain is between 1.350 kilograms. In humans and primates, sight and vision utilize about 30 different parts of the brain which together account for about half of the brain's size.
It's about 450 times as heavy as a Chihuahua
In other words, 999 kilograms is 444 times the weight of a Chihuahua, and the weight of a Chihuahua is 0.00225 times that amount.(a.k.a. Chihuahue(o) (FCI standard)
The F&d&ration Cynologique Internationale (FCI) calls for Chihuahuas to weigh about 1.5 to 3 kg. Relative to their body sizes, Chihuahuas have the largest brain size of any dog breed.
It's about 350 times as heavy as a Brick
In other words, the weight of a Brick is 0.0029 times 999 kilograms.(Standard, traditional face brick - 1,900 cu. cm (120 cu. in))
A standard, traditional face brick weighs an average of 2.9 kg. The steeple of the Church of St. Martin in Landshut, Germany is said to be the tallest brick tower in the world at a height of 130.6 m (428.5 ft) and was constructed using an estimated 650,000 bricks.
It's about 200 times as heavy as a Gallon of Paint
It's about 200 times as heavy as a Cat
It's about 150 times as heavy as a Bowling Ball
In other words, 999 kilograms is 146.8278670 times the weight of a Bowling Ball, and the weight of a Bowling Ball is 0.00681069623 times that amount.(most common selection among male bowlers)
With an allowable range of 4.989516070 kilograms, the most-preferred bowling ball weight among adult, male bowlers is 6.803885550 kilograms. Because regulation balls measure the same diameter irrespective of their weight, ball density varies by size and balls weighing less than about 5 kg (11 lbs) will float in water.