Turtleneer:
the turtleneer is a creature that can be found most commonly in valve servers, usually leaving the nest slowly and making their way to a defensive point. Once there, they build a sentry, dispenser and teleporter, only leaving their buildings to get metal. Sadly, most do not survive for long. They are an easy target for spies and demomen, making it very hard for them to stay alive.


W+M1 pyro
the name says it all, the W+M1 pyro is a common creature found almost everywhere. It is an extremely aggressive creature, and will attack (or try to attack) anything that moves. However these creatures are not very smart, as they will usually walk straight at their opponent and try to attack from a distance, often dying before they are within range.


Hoovy
The hoovy is a peaceful creature, usually wandering the map crouching holding food items or wearing mittens. If it notices you are hurt, it may give you a sandvich to help you, no matter your team. However be wary, when startled these creatures can turn extremely violent and can kill.


Croc-o-sniper
The croc-o-sniper is a species or sniper that tends to be found on many battlements on valve servers, specifically koth maps. They are ususally found standing still, scoped in, and completely oblivious to their surroundings. This makes them easy prey for most classes, as sneaking up on them is very easy.


Pybro
The Pybro is a creature usually wearing an unusual or other expensive hat, they also usually possess a degreaser and homewrecker. They tend to stick close to engineers, spychecking constantly and removing sappers. If you see one of these in the wild, don't hesitate to try and befriend it, as it can be a very helpful ally.


Trolldier
Trolldiers can be mainly found on hightower, but can also be found in other locations rarely. The trolldier is a creature that can almost always be seen flying through the air with a market gardener.
Though peaceful at times, these creatures are often hostile and hurtle through the air at breakneck speed towards their prey.


Relax-a-neers
A relax-a-neer is a docile creature that commonly sits in a chair, and does absolutely nothing else.
They are thrill seekers when it comes to choosing their spot, usually seen on cliffs or in high places.

Shpees
There are many different types of shpees, so i'll go over them all.
Common shpee
The common shpee is a creature that is very rash, and usually is at a very early age when it leaves the nest. They can be seen almost everywhere, though are VERY easy targets, and eventually mature into spies, which later also hunt down shpees.
Box shpee
The box shpee is a peaceful breed of shpee, choosing to hide instead of fighting. Rarely seen outside their boxes, they are newly discovered creatures of the badlands. They can often be found trying to blend in with their environment, using a box as their home and cover. When threatened, they may abandon their box and either fight or flee.
Shpeecrab
The shpeecrab can be found in many places. They are seen as looking up at the sky, peacefully walking along. They are becoming increasingly more threatened as engineers often do not realize they are passive. They may soon be listed as Critically endangered because of this.


Here are some shpees seen in the wild:

Dapper Intelligent Cool Scouts (DICS)
DICS are strange creatures that seem to have a death wish. They are easily spotted due to their colourful features (usually pink or green), and show no mercy towards other creatures. They are extremely compeditive and will stop at nothing to get a god-like killstreak. Y'know, I don't care if they're endangered, just kill one on sight.


Sax-o-sniper
Though they can be aggressive, Sax-o-snipers are traditionally peaceful creatures, and contact each other through their saxophones. They often use these to celebrate a kill, and are defenseless during these times.


Pyroshark
The pyroshark is an amphibious creature, but is rarely seen outside the water. They act very territorially, and will attack almost anyone who enters their waters. They are extremely deadly, and can kill most classes in less than 3 hits. However, they are often targeted by hunters hoping to take their pelts.

Here's some more info on pyrosharks:

Fat scout
The fat scout is type of hoovy that wields the natascha, shotgun/family business, and the eviction notice. They are scouts that have eaten too much, and transformed into heavies. Not really that much else to say about them.

Pyroduck
The pryoduck is an extremely peaceful creature, usually found on the lazypurple silly server, but has been sighted at other places such as badwater. They can be distinctly recognized from their yellow beak, large head, and eyes that seem to pop out of their head. They are often commonly referred to as 'bootiful duks', as a nickname.


Jessegineer
this engineer likes butts.


Alien
Looking similar to the pyroduk, Aliens are aggressive and are a threat to humanity. As such, Aliens are being hunted down and killed everywhere, but it seems as though they have sent out a distress signal.

Birdscout
Birscouts are generally aggressive towards humans and other creatures, flying through the air often celebrating after a kill. They are easy targets for snipers due to their large amount of airtime, and they usually fly alone.

Meem
Not much is known about these creatures, but they have been recorded to be both hostile and peaceful. If you see one, make sure to document it and record its behaviour, as it is suspected that each one has an entirely different personality.


Pootisbird
The pootisbird is another species of hoovy that is completely passive, and prefers to flee rather than fight. They can be spotted in high places, usually holding a sandvich and asking for a dispenser. Snipers like to hunt them as they make good target practice, and due to the fact they don't fight back upon being shot.

Statue
These creatures stand extremely still, and are extremely passive until their 'objective' has been fulfilled. They stand upright, with their arm raised just over their head, palm outstreched. Upon recieving a high-five, they will 'unfreeze' and go about and act like a sphee, or go back into their normal position.

Burds
There are currently 5 different kinds of recorded burds (medimedes, chicken keiv, freedom feathers, bird-man of aberdeen, and sir shoots-a-lot). They are all very similar but behave in slightly different ways. They are very humanoid, but are peaceful unless disturbed.

I will be adding more creatures later, if there are any I missed feel free to comment them in the comment section below!