Mouthplate

I am smiling on the outside, but crying on the inside... not that you could tell anyway.

Instead of regular human facial features, some Transformers have what looks like a plate affixed to their lower jaw, usually covering up to their nose. While no official name exists for these, they are usually called 'mouthplates ' or 'faceplates' (despite a 'regular' face once being described as a faceplate in the TV series). Two of the most famous examples are those of Generation 1's Optimus Prime and Soundwave. Sufferers of Primus apotheosis often affix themselves with unnecessary faceplates to better emulate their idol.

In earlier series, a Transformer's mouthplate moved when they spoke, as if there were a working jaw underneath. Sometimes this is proven when a character is shown without a mouthplate when they ordinarily possess one. This is especially prevalent in comics. In Victory, Robots in Disguise and the Unicron Trilogy, however, it remains static.

Fiction/Toylines

Generation 1

Optimus Prime featured a prominent mouthplate in both cartoon and toy form (as do all other G1-based toyline versions). The 20th Anniversary figure featured a mouthplate that was movable via a button on the back of his head that slightly lowered the spring-supported mouthplate to recreate the talking action seen in the cartoons.

Soundwave had a similar mouthplate, but no apparent nose (whether any of his assumed face is visible or not is debatable, considering how visor-esque his eyes are). Like Optimus, both his cartoon and toy form had the mask. No toys have yet been made with a moving mask feature.

Wheeljack's mouthplate was unique in that it was fixed, even in the cartoon. Instead of a movable mouthplate, you knew Wheeljack was speaking because his "ears" flashed.

Many early toys had mouthplates that were simply disregarded in favor of mouths in fictional appearances (barring the occasional toy-accurate rendering). Bumblebee in particular had a mask in toy form, but not in cartoon or comic form. A rare reissue of the toy features a cartoon-accurate face, however, as do most toys of him since. Conversely, as Goldbug, he featured a mask in both cartoon and toy form.

On the other hand, Superion has a faceplate on the cartoon even though his toy has a mouth.

Ultra Magnus in his newly reborn body from the Japanese continuity also feature a mouthplate.Hybrid Style Convoy Black Version

Hot Spot sometimes has a mouthplate and sometimes he doesn't.

Beast Wars

Optimus Primal was shown to have a mouthplate which would slide into place when he entered battle. This was used to reconcile the presence of an actual mouth on his animation model with the lack thereof on his toy. Later retoolings of the toy reflected the animation model.

Cybertron

The Optimus Prime animation model displays a similar setup to Optimus Primal, with a mouthplate that slides into place when entering Super Mode. However in this case the toy reflects this, featuring a gimmick that allows the face to display either configuration.

Dreamwave comics continuity

25 years before someone realized his toy has no face.

In The War Within, Bumblebee was depicted as having a removable face mask with mouthplate that resembled the original sculpt of his toy. In The Dark Ages, Jetfire was given a similar treatment with a flip-up faceguard. The Titanium Series release of this character design featured the faceguard, but it was not removable. Brawn was depicted with a removable face mask like Bumblebee's in the ongoing Generation 1 series.

IDW comics continuity

In Stormbringer, Jetfire has a removable mask with mouthplate as part of his battle gear. This feature was included in the Classics toy of this character design. Most recently in All Hail Megatron, Optimus Prime himself revealed he has a retractable mouthplate much like his Movie counterpart. This would be the first time in an official story that the G1 version of the character is portrayed as being able to remove his mouthplate, revealing that he does have a mouth underneath it (which he uses to eat some energon).

Live-action Transformers movies

Megatron did that just to piss off the purists. He's that evil.

Optimus Prime is depicted as having a combat mouthplate which closes over his normal mouth to protect his face. To date, only one of Prime's Robot Heroes figurines, Buster Optimus Prime, and the Battle Hooks redeco display his face and mouth, while all other merchandise features the plate. Blackout also has a mouthplate, seen very briefly. Bumblebee has two pieces that rest on the top of his head normally but slide down and clamp together over his whole face in battle. Bumblebee's faceplate has a very insectoid appearance, crediting his name. Jazz has a visor that protects his upper-face in combat. Ironhide also has a mouthplate similar in appearance to Optimus Prime's as shown in some concept art, however he has never officially used it on film.

In Revenge of the Fallen Optimus Prime's faceplate is smashed to pieces when he is kicked in the face by Megatron, but it is replaced when he combines with Jetfire. While not noticeable in the film, Sideswipe's Human Alliance toy confirms he has an extra layer of armor plating (which was thought to be his actual face) protecting his main face.

Transformers Animated

Most of the Autobots in Optimus Prime's crew have retractable faceplates. Optimus, Bumblebee, Sari and Prowl each have one. Sentinel Prime has one, too, though his is unique in that it covers his whole face. Among the Decepticons, Soundwave has a non-retractable mouthplate, much like his G1 predecessor's. Optimus' mouthplate flaps up and down when he talks, just like that of G1 Optimus, but none of the others' do.

Transformers Prime

Optimus Prime and Wheeljack each have a mouthplate that they slide into place over their faces whenever they enter battle.

Notes

• Fan commentator Zobovor nicknamed these distinctive items "woobers" (crediting the term to a younger relative), and the name became popular with some fans.
• Both the Armada Optimus Prime and the 20th Anniversary Optimus Prime toys have mouthplates that can move up and down when a button located on their heads is depressed, even though Armada Prime's mouthplate never moved in the series itself. Additionally, the 20th Anniversary toy has teeth (or possibly a speaker grille) hidden behind the mouthplate, in reference to Optimus Prime's battle-damaged appearance in the Generation 2 comics, though this detail cannot be seen without disassembling the entire head (or just looking down with it pulled down really far).
• The lack of a full-time mouthplate on certain characters has, in the past, been known to result in certain reactions from the fandom. Oh well.