Fancy rats:

are affectionate, playful, intelligent and clean

are as jolly and matey as a dog and as mature and independent as a cat

don't make much noise

don't smell strongly or unpleasantly: even the bucks just have a faint smell like digestive biscuits (apart from a few individuals who have BO as an abnormality); and a Finnish lady called Dr Birgitta Edelman used to have a champagne-hooded doe named Luah who had such a pleasant, floral scent that she used to be passed round to be sniffed like a pot-pourri

are very strong and hardy and are rarely ill

nearly always land on their feet (making them much safer for a child to handle than a guinea pig or hamster which is quite likely to suffer a broken back if dropped - but one still shouldn't take needless risks, as I do know of one case of a rat breaking its back in the same way)

very rarely bite

usually have bold, steady, cheerful natures

are gregarious animals who live in groups with complex social interactions, which makes them more interesting to watch than solitary species

generally make excellent mothers, competent and sensible, and do not eat their young even if disturbed (though they may have a go at eating you)

come in a variety of attractive colours, markings and coat-types

are cheap to buy and cheap to feed

Fancy rats also:

don't live very long

have enormous litters

chew things

require large, therefore expensive cages (expect to pay £30-£90)

are prone to tumours - which can nearly always be removed, but are another expense

have a powerful bite (should you be unlucky enough to get one of the rare biters)

have painfully scrabbly claws