There are loads, but I’m going to have to go with the platypus.
It has a bill like a ducks, a tail like a beavers and feet like otters. It is a mammal, but it lays eggs and its poisonous. It lactates, but doesn’t have nipples. Its teeth fall out after it it born and it can generate and detect tiny electrical currents with its bill. All very strange.
Whoa, that really is a strange looking creature! Kind of cool though.
The strangest creature I’ve ever actually seen is a slime mould (latin name: Dictyostelium discoideum, known affectionately by scientists as Dicty), which is used by some scientists for their research. It’s usually a single-celled organism, but in some situations lots of these single cells come together and make a multicellular organism. It’s pretty cool. They come together because they get attracted to a particular chemical called cAMP, and this movie shows one Dicty at the single cell stage of its life following a pipette that’s releasing cAMP: http://dictybase.org/Multimedia/development/dzl23a0.mpg
This movie shows lots of single celled Dicty coming together: http://dictybase.org/Multimedia/development/ax320x.mov
And this one shows them growing into a multicellular organism: http://dictybase.org/Multimedia/development/culm.mov
They move veeerrryy slooowwwllyy, sleep most of the day, and spend most of their lives hanging upside down. One day, I hope to go to a sloth rescue sanctuary in Costa Rica – where you can CUDDLE A BABY SLOTH!
So, even though sloths are weird, I think they are fantastic animals.