* In the ''[[WesternAnimation/AdventuresOfTheGalaxyRangers Galaxy Rangers]]'' FanFic ''Chrysalis,'' the League fleet is in a hopeless battle in the Queen's asteroid field, having been forced into a trap. However, they some critical backup courtesy of the otherwise-xenophobic [[BigCreepyCrawlies Traash]] (which even Her Majesty won't engage because they're ''just that nasty'' if crossed) and the Circle of Thought (who were isolationists, content to let the galaxy tear itself apart, so long as they were left alone...until Niko showed them that the Queen was an exile from the Circle, and thus a mistake they made).
* The MegaCrossover fic ''Odyssey'', by Drunkengrognard, has the likes of [[MagicalGirlLyricalNanoha Chrono Harlaowan]] and [[Series/StarTrekTheNextGeneration Jean-Luc Picard]], amongst others, preparing their ships for a major battle against a group of Voidspawn (essentially giant killer space squids) and planning to close the portal that they are coming from. Due to circumstances connected to the portal opening, their current location has basically turned into a multiversal thoroughfare; the suggestion is made that help could be requested throughout said multiverse in order to ward off the Voidspawn long enough for the portal to be shut. [[Franchise/StarWarsExpandedUniverse Rogue Squadron]] and the fleet they were a part of are amongst the first to answer the call, and it just gets bigger from there.
* During the FinalBattle of the MLP AU fic ''FanFic/RainboomsAndRoyalty'', the Diamond Dogs, sea ponies, and gargoyles that the Mane Six had befriended on their way through the Everfree Forest all show up to help them fight Nightmare Moon's Shadowbolt army.
* Fanfic/TakamachiNanohaOf2814: Nanoha connects with every other MagicalGirl in Japan and programs an automated message into her ring in case she was ever in serious need of help.
* In book 2 of FanFic/AGrowingAffection, when [[spoiler: Naruto is captured by the Akatsuki]] Tsunade immediately contacts the other four Kages to request aid. The Kazekage and Mizukage send troops to assist, while the Tsuchikage and Raikage only provide information. And the Raikage's assistance is especially grudging.
* In the ''FanFic/PonyPOVSeries'', during the FinalBattle of [[BadFuture Dark World]], [[spoiler: the [[BigGood Benevolent Interloper]] gets Rainbow Dash and the Princesses to return to the battlefield just in time to save the group from [[BigBad Nightmare Eclipse/Paradox]]'s PsychoRangers and assists Minty into making it to the fight as well. [[HeelFaceTurn Discord]] then [[BackupFromOtherWorld interferes to distract Eclipse]] long enough for Twilight to charge up a copied time spell from Paradox herself, that performs one of these ''across time and space'' to [[CrisisCrossover summon the G1, G2, G3, and G4 (from before the reign of Discord) Mane Casts]] to the present, allowing for ''six'' sets of Elements (including Celestia and Luna's reawakened ones) to be used at once. Finally, Twilight's parents (still plants) restrain Paradox for the final blow.]]
* Occurs multiple time in Tenhawk's Buffy Mega-Crossover [[http://grandt.com/Journey/stories/ Journeyverse]], sometimes combined with a CrisisCrossover.
** Probably the biggest example comes in City by the Bay, when Xander has been infected by a demonic virus and summons mental versions/soul fragments of everyone he's been friends/allies with over the course of the series thus far, and manages to drag along everyone they're closely tied to as well, to help him fight off the demons trying to posses him. Made all the more amusing by the fact that there had just been a backwards time-jump that removed the memories of most of those he called of ever having met him in the first place, leading to some interesting WTF moments.