Humanization

Throughout the various Transformers canon, there have been several instances of Transformers with humanistic traits and having very human actions that possibly contadict 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.

Sweating


 * In issue nine of the original G1 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 UK comic, Kup can be seen "sweating."

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.

Crying


 * Throughout Beast Wars II, several characters are seen crying in conventional anime fashion.

Intoxication


 * In the G1 episode Microbots, the Decepticons are noticeably behaving in an intoxicated fashion after consuming a high-grade energon.


 * In Beast Wars II, Galvatron gets "drunk" on numerous occasions.


 * In the UK comic, the Wreckers frequent a "bar" on Cybertron called Maccadams', where they consume high-grade energon, presumably for the purposes of getting intoxicated.

Sleeping/Dreaming/Yawning


 * In the G1 comic, Ratchet fall asleep and dreams (or rather, has a nightmare). This goes against established canon that Transformers deactivate fully rather than "sleep," a point Ratchet himself makes.


 * Beast Wars II Galvatron often nods off in a narcoleptic-like fashion.


 * In the English Headmasters dub, Galvatron yawns upon witnessing Soundwave's death (though this is most likely a translation error, in the original Japanese he roars in anger).

Teeth/tongues/eyeballs


 * Throughout the latter G1 comic and in the G2 comic, several Transformers can clearly be seen with teeth, tongues and sometimes organic eyes. This is most likely a simple stylistic choice by the artists.


 * Most of the characters in Beast Wars have teeth in robot mode. It could be theorized that they actually use them to masticate organic matter to maintain their organic parts.


 * A Legion character in the Kiss Play manga has a distinctive prehensile tongue.

Non mechanical body parts


 * In the G1 episode The Girl Who Loved Powerglide, Powerglide is seen at the end of the episode having a human heart within his chasis. This is completely nonsensical within in the context of the show (the contents of Transformers chest cavitites had been show several times before), and is probably merely meant as a one-off sight gag.


 * Alpha Trion and Wreck-Gar both sport "facial hair" in the G1 cartoon.

Sexuality
One of the most controversial aspects of Transformers is the idea of sexuality. While it is established through most canons that Transformers do not reproduce sexually, most canons 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.