Talking Lightbulb

The Talking Lightbulb is some visual effect, often a simple blinking light, that flickers away whenever a robot or computer speaks, for no reason other than to look cool. Maybe it's supposed to help the audience focus on a character that doesn't move its face when it speaks, generally because it has no face. It is often used in combination with Robo Speak. Can be justified as an user-friendly feature, since for people on both sides of Fourth Wall it's the simplest way to make obvious at a glance which one speaks when several robots, computerized appliances and talking alarm clocks are around.

Examples of Talking Lightbulb include:

Anime and Manga

In Lyrical Nanoha, if a Device has a prominent Power Crystal, it will blink and flicker in this manner when it speaks conversationally.

Film

One Trope Codifier is Robbie the Robot, who debuted in Forbidden Planet. Robbie looked like a thickset suit of armor that had had a jukebox dropped on it and, like a jukebox, had an impressive light-show built in. This included a roughly mouth-placed panel of lights that flashed in rhythm with his speech, which had a moderate Robo Speak accent.
R2-D2 in Star Wars, and C3PO's mouth.
In the Short Circuit movies, Johnny 5 has, what he refers to as, "lip lights".

Live-Action TV

The Robot from Lost in Space looked a great deal like Robbie, including the glass-dome-lightshow head and the Talking Lightbulb "mouth."
- At Paul Allen's Science Fiction Museum there's a display with Robbie and The Robot next to each other (This Troper isn't sure if they're duplicates or the originals - with Paul Allen it's hard to tell). They converse with each other on various subjects.
The ship's computer in Star Trek: The Original Series displayed an oscilloscope display when it spoke (in heavy Robo Speak). Also, in the famous episode "The Menagerie", the infirm Captain Pike, in a futuristic wheelchair, can only communicate with brainwaves translated by the wheelchair - one beep for 'yes', two for 'no'.
KITT, the robotic car from Knight Rider, had and has a Talking Lightbulb speech display in both series. The original used a series of LED lights similar to a graphic equalizer, while the new one was an extra-cool plasma display.
Daleks from Doctor Who (who are actually aliens in Powered Armor) also speak this way.
- Also the classic series incarnation of the Silurians.
- And the altered Ood, as well.
The talking toaster in early series of Red Dwarf.
London's identical, sarcastic, talking stand mirrors from The Suite Life of Zack and Cody and The Suite Life On Deck was surrounded by Talking Lightbulbs, in the manner of a typical frame-lit vanity mirror.

Western Animation

Many of the robots in Futurama have this effect. Bender is the one exception, he has a panel with a wave similar in appearance to an oscilloscope that is lipsynched to his speech. Futurama also parodied "The Menagerie"'s wheelchair when the characters had to testify in court in "Where No Fan Has Gone Before".
Karen, Plankton's computer wife in SpongeBob SquarePants, uses the oscilloscope version.
Bit from Tron can fit this. As a bit, he is only capable of two responses — "yes" or "no" — and each response is accompanied by a change of shape: a yellow octahedron for "yes", or a red spiked 3D shape for "no".
- Makes you wonder where he got his "usual" shape from. Bits are not supposed to take a third state apart from "yes" or "no".
  - Positive charge, negative charge, NO charge
    - That's a trit. Bits are "charge/yes" or "no charge/no".
Some Transformers without normal mouths are like this. The most notable is Wheeljack.
- Also (in at least some series), when a Transformer speaks in vehicle mode, whatever applicable form of headlight will flash in rhythm with the words.
The Visor Robot from Homestar Runner. An Easter Egg at the end of one cartoon starring it even revealed its voice box to be a red lightbulb after it exploded.
Whatever Happened to... Robot Jones? had the titular character's eyes flash when he spoke.

Video Games

In the Bill Nye the Science Guy computer game Stop the Rock!, when the computer you had to convince humans were worth saving from a giant asteroid spoke, the screen it was using flashed large pixels expanding from the center, with color and number corresponding to volume.
In Mass Effect Tali'Zorah's helmet (and presumably all Quarian suits) has a light that flashes in sync with her speech. Justified in that Quarian helmets obscure the face and as they wear them near-constantly it would make group conversations highly confusing.
- The Volus also have flashing lights, for exactly the same reason.
Clanky from Backyard Sports has a lightbulb on his head which flashes in sync whenever Clanky "speaks."
Halo. The monitors' eye light in the center of their 'body' flashes in sync with their speech. This light can also apparently be used as a weapon

Real Life

Ringing Lightbulbs are standard equipment for the residences of the hearing-impaired. Many flash in different patterns or colors, to distinguish whether it's the doorbell, the telephone, or the fire alarm that's out to attract the occupant's attention.