This trope generally arises in situations where The Hero and the Big Bad (or some other substitute boss villain) are staring each other down, ready to engage in mortal combat. The Big Bad challenges the Hero to a duel, but then instead of said fight being one-on-one, as the viewer and the Hero might expect, the villain promptly yells for his ... GUARDS!
May result in the invocation of Big Damn Heroes if the good guy is in too deep. Conversely, should the hero do better than expected, the villain may realize that he needs reinforcements and act accordingly. Alternately, it could show that the villain is Dangerously Genre Savvy enough to know not to fight the hero one-on-one when he can bring in his minions to support him.
Can overlap with Bait-and-Switch Boss in video games; however, typically, when invoking this trope the villain fights alongside his Mooks or at least remains present to observe the fight (and hopefully the hero's demise). May even cross-pollinate with Summon Bigger Fish if the hero seriously outclasses the villain and/or the Mooks are sufficiently powerful in their own right.
The villain may be disappointed if the fight is subject to Conservation of Ninjutsu and/or Mook Chivalry, or if he's dealing with an Invincible Hero. This is the antitrope of Leave Him to Me.
Neo's first fight with Agent Smith in The Matrix Reloaded may also be this trope, although Smith multiplies himself rather than calling for subordinates.
In Kill Bill Volume One, O-Ren seems ready to take on the Bride in single combat, but then has her personal army, the Crazy 88, soften her up first.
Inverted in the film version of Harry Potter and the Deathly Hallows, where after Harry reveals himself to then-headmaster Snape, the Order of the Phoenix are the ones barging in en masse when Harry seems set to face down Snape alone.
The Avengers has Black Widow visiting Bruce Banner with assurances it's only the two of them. Then he shows a flash of anger because he "wanted to see what she'd do." (What she does is immediately point a handgun at him.) Once it's clear he's not turning into an enormous green rage-monster, she tells the veritable SWAT team outside that they can stand down.
Bruce Banner: "Just you and me", huh?
Literature
In the Corum series, Corum's meets Prince Gaynor the Damned for a showdown, and it goes like this:
A spaceborne version of this occurs in Battlestar Galactica, during the escape from New Caprica at the start of the third season. The Galactica jumps into orbit alone, expecting to face two Cylon Basestars, whereupon two more promptly jump in from elsewhere and join what swiftly degenerates into a Curb-Stomp Battle. That is, until Apollo decides to save the day by arriving with thePegasus, allowing the Galactica to jump to safety before the battle is concluded in a decidedly spectacular fashion.
In Assassin's Creed 2 Ezio does this in the 2nd to final boss fight. The same way the last boss of the previous game did.
In the trailer for Assassin's Creed: Brotherhood, Ezio makes his way through a cordon of guards to confront the son of Rodrigo Borgia, the Big Bad of the previous game. Borgia Jr. mocks Ezio and promptly summons a dozen heavily-armed Papal guardsmen, whereupon Ezio's allies also emerge from the crowd and the two groups charge at one another in combat.
It's played straight when you finally track Cesare down, though Ezio's Assassins being unavailable is justified, what with him being in Spain.
World of Warcraft Culling of Stratholme instance, Arthas faces down Mal'ganis proclaiming the fight will be "Just between you and me." Apparently Mal'ganis is meant to ignore the five people standing with Arty. This is particularly absurd because Mal'ganis will spend the entire fight not only ignoring Arthas and attacking the tank, but if the tank's doing their job, actually facing in the opposite direction from Arthas so the rest of the party doesn't get blasted with his Carrion Swarm spell.
To be fair, not only is that non-canon, he did fight him one on one in the original timeline.
Half-subverted as a part of the Sequential end boss of Final Fantasy VIII The last boss's first One-Winged Angel is to summon a GF for the party to fight, Then as her second OWA, she merges with it into a horrible half-breed.
In Final Fantasy X in the first boss battle with Seymour, he fights alongside two of his guado servants. When you defeat them, he relies on summoning Anima to fight for him, though that is justified since he's a Summoner.
Judge Ghis in Final Fantasy XII Also comes with a couple of mooks for your inconvenience.
In Diablo Singleplayer the Archbishop Lazarus is accmpanied by two named Witches, while this technically wouldn't fit under the trope as you could consider it a trio instead of a boss with mooks, The pack of Hell Spawn and Advocates that emerge from a disappearing wall does most definatively count.
Also worthy of a mention Diablo himself is in a room with lots of high level mooks, though he can be triggered by way of ranged attacks that leaves the mooks out of the fight.
Actually, most all of the unique monsters tied to quests come with a cohort, including notably The Skeleton King and The Warlord of Blood. All the regular uniques come inside a group of regular monsters of it's type, though that's more of an inversion as the mooks come with a boss rather than the boss bring along some mooks.
Security Chief Vince, from Metal Gear Ac!d 2. When Snake and Venus encounter him for the second time, he mentions before the fight that this time he brought backup, at which point several of his men enter the battlefield.
Knights of the Old Republic has a somewhat lengthy set of sidequests that involve killing off the three leaders of the Genoharadan, a shadowy organization that influenced the galaxy through assassination, among other things. After killing the leaders, the man who gave you the quests, Hulas, reveals that he was the fourth leader and that he used you to consolidate his power by killing his rivals. If you don't take kindly to being used like that, you can challenge him to a duel, for which he insists you come alone. Hulas brings two lackeys with him, but you can display some Genre Savviness of your own and bring your party members. Hulas actually expects you to not play by the rules, expressing surprise if you show up alone, and saying "I hoped you'd be gullible but clearly you're not" if you bring your friends.
In Portal2, when you arrive in GLaDOS's chamber for a confrontation with her, she reveals that she has several turrets standing by to kill you dead.
Occurs during the Dragon Ball Z Abridged Christmas Special. Turles, the weekly villain of the piece, attempts to overwhelm Goku with all five of his supporting minions. It doesn't end well for the minions.
