Adults probably seem kind of like monsters to small children. Besides the obvious things, like that we are large and talk in loud, deep voices; we also do weird, dangerous things in the kitchen like boil water and cook food, which we then eat as hot as we can handle it. Hot coffee, hot soup, food with molten cheese toppings and such probably seem like monster food to babies; which we gobble up with huge bites.
But for that matter, babies seem like weird little creatures to older children. Especially newborns who can't do much except cry and just lie there like blobs. Adults are always boiling their bottles, wrapping them delicately in sterilized fabrics and such. And they smell bad quite often.
Like adults, really, if we're being honest.