How realistic are these tropes after all?

I'm gonna start by asking if a particular iteration of Dual Wielding has ever happened outside fiction.

This wiki has explained very well why Dual Wielding has never been used extensively in real life: most people can use only one hand at a time, it needs a lot of training and most weapons will bump into each other, and that's for melee weapons: Guns Akimbo presents another set of challenges that make it impractical.
Even the supposed advantages in fiction of Dual Wielding (increased damage and/or attacking speed) aren't that real, so it just makes you a worse fighter.
At the same time, this wiki has also explained that, since shields could be classified as weapons too, not only is Knightly Sword and Shield an example of Dual Wielding, it's its most (and only) effective and enduring form of it.

And some characters go a step above that, and dual-wield shields. SHIELDS.
This isn't super common in fiction (with all that implies...), but I can list a few examples: Falinks has small shields for arms; Ryuki's Guardvent summons a pair of shields; there was a 70s Super Robot anime (don't remember the name now) where the mecha also dual-wielded spiked, buzz-saw like throwable shields; and apparently Dungeons & Dragons and Final Fantasy can occasionally let you dual-wield shields.

Has this ever happened in real life, that we know of? Can this ever happen in real life? I know I said earlier that shields can be weapons too, but using two shields at a time still sounds way too impractical.
I guess some Nuragic bronze figures do dual-wield shields, but at the same time they are some kind of Multi-Armed and Dangerous warriors, wielding a pair of shields together with a pair of conventional weapons, which isn't what I was looking for.

What would happen, realistically, if a person wielded nothing but a pair of shields? Would they be more protected than just using one shield? Is it better to use different kinds of shields, instead of using two shields of the same type as in fiction?
Who even first thought of this?

I tried looking elsewhere: Wikipedia doesn't seem to mention Dual Wielding shields, and I couldn't find any scientific papers about Dual Wielding at all.

The purest form of Dual Wielding in terms of identical weapons have probably had little to no open combat use, though plenty of katas and demonstration forms exist simply because weapon familiarity sometimes demands training beyond realism. Specific close combat and other guerilla tactics do exist, typically with small knives that would benefit the person anticipating multiple opponents. There is also many examples of a primary weapon and a support weapon, such as a 3-4 foot long sword with a 1-2 foot long parrying or disarming weapon, and so their usage is not flailing both in equal tandem.

Thanks, but have you heard or seen anything about what happens when one dual wields shields?

Most practical dual wielding styles are less two weapons than an offensive weapon and a defensive one. Typically a sword and a parrying dagger, but that dagger could also be used on the attack if the chance arose. So it could be thought of as a lighter, more dextrous type of shield (and one useless against projectiles, so much depends on what armour one is wearing).

Videogames don't reflect this well, for various reasons: the player's perspective and control scheme makes it difficult to implement any realistic parry, so instead avoiding an attack is either by moving out of its way or with a simple button to parry, with the timing being what matters. Many games where the player controls a party expect a designated tank to take the hits while others whittle down the enemy, because realistic death or dismemberment from a single stroke doesn't give enough time for tactics. Games like Pillars of Eternity could have implemented dual wielding as a defensive option, but it's an offensive one likely because "shields = defense, weapons = offense" is more intuitive and allows more varied builds.

I will just add that the thread is badly titled. If you want to talk about a particular trope, like Dual Wielding, it should be in the title.

While I started this thread to discuss Dual Wielding, I intentionally left the title vague so that other users could ask about the realism of other tropes after we're done with Dual Wielding.

I can think of only three situations were one might have conceivably dual wielded shield from least to most likely.

1) There might a weird edge case where you're anchoring a shield wall where oddities in the terrain or obstacles mean you might realistically need to guard in two directions and it might be worth it to hold a second shield and let the second row hard handles the stabby part... but this would be rare and situational.

2) Trying to cover someone else so they can use both hands to pull a fallen comrade to safety/better cover. Again short term and situation specific.

3) is proceeded by the words: Ho lads! Hold my ale and watch this.

4) The shields aren't very good quality, so you want a second one handy when the first starts getting hacked apart.