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 nine of the original Generation 1 comic, Frenzy 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."
Like most Anime clishes the "Giant Bead of Sweat" was applied to Transformers.
Spitting
Throughout his term on the Marvel UK comic letters page, Soundwave would regularly spit oil onto the ground whenever humans were mentioned. How he did this through his mouthplate is unknown.
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".
Throughout Beast Wars II and Robots in Disguise, and occasionally in the Armada cartoon, several characters are seen crying in conventional anime fashion.
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.
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.
Body parts
Teeth/tongues/eyeballs
A little too friendly, there, Megatron...
The Generation 1 cartoon series is the only major piece of fiction to not present Transformers as possessing teeth and/or tongues. The features appear in both the Marvel and Dreamwave comics, the Beast Wars and Beast Machines animated series (where teeth would even be knocked out on occasion), the Robots in Disguise cartoon, and the Unicron Trilogy cartoons and comics.
One of the most recent examples to carry on this tradition is the Kiss Players manga, in which a Legion character is equipped with a distinctive prehensile tongue.
Questionable body parts
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 cavitites 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, Megatron has been shown to sleep in the command chair of the Darkside, while his dino head mounted on the end of his arm stays awake, looks around, and smiles slyly. I wonder what it's thinking about...
Beast Wars II Galvatron often nods off in a narcoleptic-like fashion.
ArmadaCyclonus is quite fond of catching forty winks when possible. Scavenger did the same on one occasion.
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).
The G1 cartoon brought the first official female Autobots into the canon, including Elita One and Arcee. The characters are noticably 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.
