What would you do if you had the opportunity to change your life? Not just where you live or who you hang out with, but your past, present, and future? Sounds like it might be pretty cool, right? Well, that's what Jake thought. He thought it might be easier if the Animorphs had never existed. If they'd never met Elfangor. If they all had the chance to be "normal" kids.
Jake gets his wish.
But things aren't quite as simple as they seem. Just because the Animorphs no longer exist doesn't mean the Yeerks no longer exist. Except now Jake, Rachel, Tobias, Cassie, and Marco can't morph. They don't even know the Yeerks are out there. And it's not such a wonderful life...
After a particularly vicious battle, Crayak sends the Drode to tempt Jake into accepting an alternate reality in which the Animorphs did not walk home through the abandoned construction site, did not meet Elfangor, and did not become Animorphs.
The results are drastic: a friendless Tobias joins The Sharing, and is infested by a Yeerk who is later revealed as a spy for Visser One, and is killed. Marco- now dating Rachel in this world- runs into his mother, but she escapes before he can confront her. Jake discovers that his brother Tom is involved with dangerous dealings after a Yeerk security leak. And all the while, Cassie has a strong feeling that all is not right. Ax manages to escape from his Dome Ship, and begins to warn the people of Earth about the Yeerk presence.
The Yeerk response is immediate: they abandon their silent invasion and launch all-out warfare. In the ensuing chaos, Marco, Rachel and Cassie are all killed, while Jake and Ax meet up and manage to kill Visser Three by ramming the Blade Ship with a stolen Bug Fighter. They take control of the Blade ship and plan to use it to destroy the Yeerk Pool Ship, at which point the Drode and the Ellimist interrupt the timeline, returning the deceased characters to life and returning everyone's memories. The Drode complains that the events in this timeline are doomed to cause failure, and the Ellimist reveals that Cassie is an anomaly, a rare individual who is grounded in the true timeline and will disrupt any other timelines that try to take its place- explaining Cassie's feeling that something was not right. It is also revealed that The Ellimist manipulated events (or as the Drode exclaimes in disgust "stacked the deck") to ensure that Cassie, Marco, Tobias, and Ax- the anomaly, the son of Visser One's host, Elfangor's paradoxical son and Elfangor's brother- were all Animorphs; Jake and Rachel apparently became Animorphs through chance alone.
The Ellimist restores everything to as it was - with only Cassie retaining even a vague memory of this new timeline, preferring that Jake and Tobias not know how they gave in to the Drode and the Yeerks respectively - and this time around the Drode decides not to try to tempt Jake into accepting the alternate reality.
- This is the one book in the series where the story was published after the TV show had already created an episode with the same story . At the time, this book had still yet to be written, so the TV show had no specific things to adapt from. However, it should be noted that both the TV show and the book portrayed the same what-if "What a Wonderful Life" scenario before turning it upside down on our heroes.
- Both the episode and the book start out the same, with Jake wishing that he had never crossed the construction site that night, and gets that wish granted. The events that take place in both stories have their similarities, but also major differences as well (Characters dying, full out invasion vs being controlled, etc). It should also be noted that both stories were created by pure coincidence at the time. K.A. did not take the idea from the show, nor the other way around.
- ANIBASE: One revelation in this book is that Cassie is an "anomaly", and, as such, is capable of holding the real timeline in place so that a false timeline will degrade over time. But Katherine didn't come up with this concept until the book was almost finished. She said: "Sometimes I know what I'm doing all the way through a book, and sometimes I don't figure it out till it's almost over. I was about ten pages from the end [of Megamorphs #4] before I thought, oh, that's how we'll do it! Then I had to 'back-write' to get it all to make sense. Yet another lesson in why you shouldn't mess with time travel."
- ANIBASE: This book marks a change in who portrays the characters on the covers. The models for Jake , Rachel , Tobias , and Marco all went off to college and new, younger models were hired to portray them. Only Biko, the Cassie model, went to a school close enough to continue on as a cover model, and, as a result, she is the only Animorphs model to have been on every cover since the beginning!
- ANIBASE: Tobias, lonely and bullied by many (but mostly by a pair of thugs named Andy and Tap-Tap), turns to the Sharing to find an escape from his messed up life. It is there that he meets Bill, his advisor and the guy that convinces him to become a full member. Little does Tobias know that becoming a full member means letting a Yeerk named Odret 177 take over his body. A Yeerk that just so happens to be an ally of Visser One, and therefore a target by Visser Three....
- The Megamorphs aren't the only books in the series that provide narration from more than one Animorph at a time. In Animorphs #19: The Departure , Jake provided narration for at least one chapter when Cassie couldn't. In #54: The Beginning , the book itself acted as a Megamorph by giving narration from most of the Animorphs one last time before the series ended. Lastly, The Hork-Bajir Chronicles , also provided a narration from both Aldrea and the Yeerk Esplin (Later Visser Three)