There are numerous differences.
A platypus is a monotreme.
A male platypus could kill a cat. It would have enough venom in its spur to achieve this. A female platypus does not have a venomous spur.
The platypus's spur is sharp and attached to a venom gland in the platypus's thigh. The echidna's spur is blunt, and is not attached to a functional venom gland.
whiskers
they both have mammary glands which they use to feed their young
the "m"
One is real, and one is not. There is no such thing as a spoon billed platypus.
They give birth to live babies, but the platypus lays eggs.
A big cat can roar but a little cat can only purr
there isnt a difference moron
There is a 10 hour difference.
cat is a carnivore but sheep is a herbivore