Most TCPs will have two spots or markings on the front of their face meant to represent eyes, and an abstract-type's eyespots even have eyelids as well as a moving pupil. These markings do not actually function as eyes, however- TCPs can still see without them. If a TCP's eyespots are removed, or the TCP is a certain type that does not possess eyespots, it can still see perfectly fine. TCP vision appears to be restricted to a field of vision consistent with the location of its eyespots (or the spot on the face where they would be), even if the eyespots themselves do not actually function as eyes. Ear nubs work in the same fashion- they are simply lumps of flesh designed to resemble cat ears, and are unimportant for actual hearing. All TCPs possess monocular vision that originates from an ambiguous point on the front of the face, as well as directional hearing.

All TCPs have some form of fluid within their bodies, usually in the form of a fluid core, a central mass of fluid within the TCP's body. Fluid is usually about the consistency of molasses, although it can be different depending on the type of TCP. While TCPs do not need to eat or breathe in order to survive, they are somehow dependent on fluid. While fluid does not need to be actively replenished or fueled in any way, if a TCP loses too much of it, it can become weakened, sick, or even die. Fluid is also closely tied to a TCP's physiology- in some cases, altering the chemical makeup of a TCP's fluid can create drastic changes in a TCP's body.

Most TCPs have some sort of skin or outer layer that protects their fluid core from outside harm. The actual makeup of TCP skin can vary wildly depending on the type, but standard TCP skin is rubbery to the touch and slightly stretchy. TCPs appear to be able to smell and taste to a certain degree through their skin, but not as well as beings with actual noses or tongues. Food-type TCPs can break off parts of their body at will, which any other TCP can then absorb through their skin in order to heal or provide another status effect. While TCPs can absorb food-type material through any part of their body, most find it much easier to absorb it through their face- in fact, it is possible to force a TCP to eat by mashing food-type material up against its face.

All TCPs speak in abstract vocalizations that vary depending on their type. A bird-type might speak in chirps and whistles, while a truck-type might speak in low grumbles and hums. Despite the fact that no TCP speaks in actual words, anyone listening is able to get a general idea of what the TCP is saying. It is unknown how exactly we understand TCP speech- most describe it as “just sort of a gut feeling”. Most TCPs appear to be able to understand both spoken or written speech, and if taught to do so, can write in legible text.

All TCPs possess some kind of ability. It is largely unknown where these abilities come from or how they work, but in most cases the TCP is instinctively aware of what its ability is and has a general sense of what it does. TCPs that have an active ability (an ability one can choose to activate at any given time, rather than an ability that is active all the time) usually have to sacrifice health in order to use it, and repeated use over a short period of time, even with food-type material to regain health, can be incredibly exhausting for most TCPs. TCPs with passive abilities do not appear to have any sort of bodily strain as a result of the ability being constantly active, and in fact, most don't even notice it until reminded.

Whenever a TCP kills another TCP, the killer is afflicted with a mark. Marks are harmless and purely cosmetic, appearing as a colored streak emanating from one eyespot (or equivalent facial feature). The appearance of marks varies based on the circumstances surrounding the death- a more intense death will generate a larger mark, whereas a quieter death will generate a smaller mark. The more the TCP regrets the kill, the more broken up the corresponding mark will become. Most marks are black in color, but in the case of hybrid TCPs whose components had marks, the marks will change to a color corresponding with the original owner.

The 'rules' for acquiring a mark are somewhat difficult to determine, but the current theory is that acquiring a mark is based on a combination of intent and cause- intent being whether or not the TCP was trying to kill the victim, and cause being how directly the TCP contributed to the victim's death. Generally, having either cause or intent- or both- will generate a mark. A TCP that slips poison into a fruit knowing that it would later be used in a sandwich and fed to a specific TCP would have intent, but not cause, since it killed the TCP using an indirect method. A TCP that slips while holding a knife and stabs another TCP by accident would have cause, but not intent- and would gain a mark from the accident.

Marks cannot be removed, and attempting to place anything on top of them to cover them up will result in the material being singed and melted, as if burned by acid. If a TCP loses the body part bearing the mark, the mark will reappear somewhere else, unchanged. TCPs have an innate sense of what marks are, although they do not seem to know the meaning of differently shaped marks- their knowledge seems limited to “marks mean killing”.