Throughout the various Transformers canon, there have been several instances of Transformers with humanistic traits and having very human actions that possibly conflict with their status as mechanical robots. Many of these instances can be dismissed as stylistic choices by the artists or as gags not to be taken seriously.
In issue twelve of the original Generation 1 comic, Rumble is seen leaking lubricant from his head during a stressful confrontation with Shockwave (as Shockwave points out), in a manner resembling sweating.
Numerous times in the Marvel UK comic, Kup can be seen "sweating."
Robots in Disguise and Armada featured Transformers displaying the traditional anime "sweatdrop," a giant bead of liquid appearing at the side of the head to convey embarrassment or exasperation.
Coughing
In the G1 episode Roll For It, when the Autobots emerge from the ruins of a demolished antimatter laboratory, they are coughing.
In Beast Wars, Megatron begins to cough for no reason while making a triumphant speech. Much like Powerglide's "heart", this could be a one-shot joke. He also coughs while sleeping.
In the episode Mortal Combat in Transformers Armada, right after Optimus Prime says "I wish I could accommodate you", he coughs silently.
Breathing
When being constricted by a python, Cheetor says he can't breathe. Dark Voyage
In an Energon episode, Jetfire instructs Ironhide that they have to synchronize their breathing before they can powerlink.
Bumblebee was shown to be breathing heavily after trying to chase down Blurr. Velocity
Spitting
Throughout his term on the Marvel UK comic letters page, Soundwave would regularly say "(Puttup)" after mentioning the Autobots or an Autobot's name to represent him spitting in disgust. This habit made an in-story appearance, with him spitting at Robot-Master despite his mouthplate.
In issue 72 of the Marvel US comics, after Nightbeat escapes from the Decepticons's New Jersey base via a sewer, he spits as he complains about their poor choice of backdoor.
In the Beast Wars episode "Tangled Web", Quickstrike "spat" after reissuing his challenge to tangle with Silverbolt, despite the fact that, like Soundwave, he has no apparent mouth.
Crying
Tissue: desired.A twinkle of light that may not literally be a tear, but is clearly intended to imply one, can be seen in Omega Supreme's eye at the end of "The Secret of Omega Supreme".
In The Burden Hardest to Bear, Scourge had tears falling from his eyes, presumably in pain, during his monstrous disfigurement after he gains the power of the Matrix.
As he mourns his dead friend Snowstalker and decides he can never fight again, Tigatron cries a single tear in beast mode.
Throughout Beast Wars II and Robots in Disguise, and occasionally in the Armada cartoon, several characters are seen crying in hyperbolic anime fashion.
Tears can be seen welling up in Ironhide's eyes and falling to the ground in Energon as he mourns a fallen comrade.
In Beast Wars, the Maximals and Predacons are shown to eat:
Tarantulas even displays something of a voracious appetite, eating rats and leaving webs to catch prey. At one point he captures Cheetor and prepares to drain his fluids, claiming that it is the act he prefers over the nourishment (which adds just another level of creepy to the already creepy Tarantulas) The Web
Also in Beast Machines, Optimus Primal wants to eat the underground tree's fruit; Cheetor protests that "we don't eat food, we process energon--PERIOD!", but is overruled. Forbidden Fruit
Flatulence
In the Beast Wars episode "The Low Road", Rhinox lets out an extreme amount of flatulence after consuming wild bean vines. This could be due to Maximals having organic parts in their makeup.
Also in Beast Wars, in the episode "Bad Spark", Cheetor also lets out flatulence, blaming it on a large buildup of energy from his Transmetal body.
Urination
Tasmania Kid urinated (in beast mode) to put out a fire.
Bumblebee performed a similar action on Agent Simmons, by popping off his automobile oil filter in robot mode. Optimus Prime claims that he was just "lubricating" him. Presumably, this action was inspired from witnessing a similar incident.
Intoxication
In the G1 cartoon episode "Microbots", the Decepticons are noticeably behaving in an intoxicated fashion after consuming high-grade energon. Powerglide referred to this as "over-energizing".
In Beast Wars II, Galvatron gets "drunk" on numerous occasions.
In the UK comic, the Wreckers frequent a "bar" on Cybertron called Maccadam's Old Oil House, where they consume high-grade energon, presumably for the purposes of getting intoxicated. Dreadwind and Darkwing paid a visit to this establishment in a later story, and got so hammered that they didn't even notice Quickswitch fighting with some Mecannibals.
In the episode Auto Berserk, Optimus Prime's eyes are closed (apparently to shield them against the smoke) much like a human's when Autobots stagger out of the fire and smoke of the Negavator's destruction.
Deathsaurus once got a cold causing him to cough and have a fever in an episode from Victory manga.
One of the most prevalent examples of this tradition is the Kiss Players manga, in which a Legion character is equipped with a distinctive prehensile (and phallic) tongue.
Not Astroboy, we swear!Predaking: All brawn AND brains!
Nearly all Transformers seem to possess noses for no discernable functional reason.
In the G1 episode "The Girl Who Loved Powerglide", Powerglide is seen at the end of the episode having the LED outline of a cartoon heart within his chasis. This is somewhat nonsensical within in the context of the show (the contents of Transformers chest cavities had been shown several times before), and is probably merely meant as a one-off sight gag.
Predaking (possibly brought back from the dead) has an organic brain when he is sliced in half in Zone.
Other biological functions
Sleep
In the G1 comic, Ratchet falls asleep and dreams (or rather, has a nightmare). This goes against established canon for that continuity that Transformers deactivate fully rather than "sleep," a point Ratchet himself makes.
In the Generation 2comic, Kup attempts to rouse a vision-struck Optimus Prime by urging him to "wake up" -- then reminds himself that "we don't sleep!"
In Beast Wars, it has been firmly established that (perhaps partially due to their organic components), all Transformers within the cartoon sleep. Some prime examples of this are:
Megatron has been shown to sleep in the command chair of the Darksyde, while his dino head mounted on the end of his arm stays awake, looks around, and smiles slyly. Wonder what it thinks about...
Cheetor has been shown asleep at many points, complete with (occasionally prophetic) dreams. In Feral Scream Part 2, he also purrs when he's asleep. How cute!
In "Call of the Wild", the Maximals are kept awake for two days by the Predacons' non-stop attacks on their base, which exacerbate their beast instincts overriding their logic circuits.
ArmadaCyclonus is quite fond of catching forty winks when possible. Scavenger did the same on one occasion. Armada Megatron was also seen asleep twice in the episode "Rebellion".
AnimatedRatchet enters a form of sleep he calls a "stasis nap", during which he gets several parking tickets. Transform and Roll Out!
Sexuality
One of the most controversial aspects of Transformers is the idea of sexuality. While it is established in most continuities that Transformers do not reproduce sexually, most continuities nonetheless have distinctive male and female characters (with the notable exception of the G1 comic, which explicitly states there is no sexual distinction).
Sorry Sideburn, I don't think Wedge rolls that way.
The G1 cartoon brought the first official female Autobots into the canon, including Elita One and Arcee. The characters are noticeably more feminine in design and have clearly defined romantic relationships with male Autobots.
The issue becomes more complicated in Beast Wars, where the sexuality line is clearly defined (Blackarachnia has a particularly well defined female figure, including what appears to be an ample bosom). It is hinted on occasion that the robots may engage in activities resembling human sex acts. Rattrap slyly makes a double entendre to Silverbolt regarding his suspected kinky activities with Predacon Blackarachnia, and later makes a comment about going to what sounds like a Cybertonian version of a strip club. In the Metals dub, Rattrap, thinking himself about to be stabbed by Dinobot, asked him to "be gentle, because I've heard the first time can hurt."
In the original Japanese version of Energon, Mirage displays romantic interest in Galvatron, causing his comrades to regard him with minor confusion. The Energon dub seemed to do its best to skirt around this issue, with Mirage's exclamations either being about different things entirely or simple cheering on of his leader - but they couldn't do anything about the hands-clasped-beside-his-head-while-doe-eyed expressions, or the one time that he pirouetted and struck a pose while surrounded by a giant glowing pink heart. Why, Japan?
