Firstly, we’d have the following setup (SPOILERS if you haven’t played any of the Mass Effect games): Full Paragon!Shepard.
Kaiden dies a hero on Virmire.
Citadel council saved.
Khalisah treated respectfully throughout the series.
Conrad guided to right path and becomes useful.
Tali romanced from events of ME2 onward.
Ashely romanced in one, managed to remain friends with her. Ashley is alive at the end of the game.
Thane kills Kai Leng, goes into coma but is still alive. (Change of events from actual game.)
Tali manages to save Legion, creating a copy of his mind and experiences (but not his soul) to disperse to the Geth, giving them Legion-level freedom of thought and intelligence, but keeping Legion alive. (Change of events from actual game.)
Shepard goes WITH Mordin up the tower on Tuchanka, manages to save him before everything goes boom. (Change of events from actual game.)
Samara’s suicide prevented.
Asari homeworld saved with help from Aria’s added forces. Nyreen’s death prevented as well. (Change of events from actual game.)
All DLC missions completed.
Kasumi alive, black box with her boyfriend in it destroyed.
Wrex and Grunt alive.
Garrus, Jacob, Liara, Zaeed, Vega, and Aria alive.
Everyone saved in Suicide Mission during events of 2, Chakwas still on good terms with Shepard.
Saren and The Illusive Man talked into killing themselves.
Jack alive and still human.
Javik is not suicidal.
Synthesis ending chosen.
God Machine Shepard creates a new body for his human consciousness, allowing him to remain with Tali in the remade galaxy.
Joker’s disease cured by new techno-organic state, starts a romantic relationship with EDI and can actually fight now, although he prefers not to.
Thane revived and cured by Synthesis.
(Basically, the Perfect Ending that Bioware never gave us.)
Now that the setup’s out of the way, here’s where the Care Bears become involved.
In the Waking Nightmares Remix edition, they’re actually the Volus. They’ve been working discreetly to help people, presenting themselves as the unpleasant Volus (some even going in for biotic implants, using short Care Bear Stare bursts to get the doctors to think that they look like something else).
By sheer accident, the truth is revealed about the Volus by Zaeed, Shepard and company drafted by the Council to re-examine the ‘Volus homeworld,’ actually a disguised Care-A-Lot, intense illusory magic used to disguise everyone’s perceptions. Several members of the crew (including Grunt), would be overcome by the cuteness of the Care Bears.
There’s a problem, though. The Citadel Council has been plagued by nightmares lately, and it’s been affecting their decision-making capability. What they don’t know yet is that a long-forgotten monster on Earth has been reawakened by the Synthesis, and has targeted the Council.
The Slenderman has been revived.
And the Synthesis has made him more powerful than before. Now machines don’t short out in his presence. Now he can command them as well as he commands people…
Anyway, that’s my idea for a Mass Effect/Care Bears version of Waking Nightmares. Not bad for something off of the top of my head, huh? XD