[[http://wiki.paradoxmod.com/index.php?title=A_Red_Letter_Day A Red Letter Day]] is an entirely self-indulgent {{Crossover}} {{Fanfic}} between RedAlert3Paradox and Franchise/MassEffect, written by the creator of the former and inspired by Peptuck's fic Fanfic/{{Renegade}}.

Set in 2185, humanity has just been granted an embassy on Citadel by the Council. However, issues arise immediately, as humanity has no single representative organization, still being divided between the Soviet Union and Allied Nations (now TheFederation). Things quickly take a turn for the worse as Eden Prime comes under attack from a mysterious force, and it comes down to one Commissar-Commander Shepard to retrieve a Prothean artifact and hold a forge a tenuous alliance.

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!! This fic provides examples of:

* CurbStompBattle: The First Contract War for humans, Sovereign against the combined fleets.
* DisproportionateRetribution: What humanity did to the Turians in the First Contact War, which scared the bejesus out of the Council.
* ForeverWar: Between the Allies and Soviet, though there are noted "Cold War" and "Hot War" periods.
** Made "Better" because it's implied that there really isn't that much of a difference between the two sides at the most basic level, their main point of contention being "Those guys aren't us."
* HumansAreCthulhu: Well, our technology is. How would you feel if your relatively hard sci-fi universe got overturned by people with psychic powers, time travel, practical invincibility and space-time bending?
** Even better, our computer technologies are laughably primitive in comparison to the Citadel's, and yet we can ''still'' do all of those things with our tech. Case in point? When humans first came to the Citadel to exchange data, they brought ''punch cards and magnetic reels.'' And yet this species is capable of casual time travel, stealth in space, mass cloning...
* HumansAreWarriors
* ImHavingSoulPains: When Shepard invaded the mind of the indoctrinated clone trooper, it did something ''bad'' to her nervous system.
* LensmanArmsRace: Still on between the Allies and Soviets, which has lead to technologies that, frankly, don't make a lot of sense to outsiders anymore.
** Hell, Shepard even says that certain technologies (specifically, Time Travel) don't make sense to those on the ''inside.'' Kaiden openly admits that one or two people a year go insane from delving too deeply into the mysteries of time.
* PsychicPowers: Commonplace by 2185 and essentially replacing biotics for human beings.
* SpaceFillingEmpire: Both the Allies and Soviets did this until they were the only ones left.
* TimeTravel: Of the StableTimeLoop variety. The Allies use this so frequently and casually that humans are completely desensitized to it.
* WorldWarWhatever: At one point, Shepard fears accidentally starting World War ''Six''.