When Brian approaches Stewie about helping him find a tennis ball he'd buried, Stewie asks if Brian remembers the date that he lost it. Brian tells him that he buried it on January 31, 1999 (the day that the first episode of the series originally aired). Using Stewie's time machine to travel back to that date, the two soon come upon the Griffin family, but notice that their past looks more strange than they remembered it: The family continually pauses for cutaways, and Meg's voice sounds different. Telling Brian that he mustn't alter the past by getting the tennis ball and that he should instead memorize its location, Stewie goes into his room to set up their return to the present before Past Stewie suddenly enters. The two Stewies then meet, and Stewie tells Brian to come out from his hiding place after explaining himself to Past Stewie. However, Brian fell onto to Past Peter's car as he drives to the bachelor party at past Glenn Quagmire's house. Stewie finds Brian and the two then attempt to return to the present, but find that the transportation device's batteries are running low and moved only a bit forward in time. Later, the two manage to take advantage of Peter dumping his extra welfare money out of a blimp above Super Bowl XXXIII to collect the money needed to purchase new batteries. It was only after the two return to the present that Stewie learns that Brian told his past self about the September 11 attacks ahead of time, allowing Past Brian to stop the event and alter the timeline as a result.
While watching the local news, it is also discovered that former President George W. Bush, who has lost the 2004 election, has returned to Texas and seceded from the United States, along with the rest of the southern United States, resulting in a second Civil War. Brian insists that things will still be better in the end, but when they travel five years into the future they find a computer generated post-apocalyptic future caused by nuclear attacks all across the United States. Admitting that he made a mistake, Brian asks how the situation can be resolved. The two then return to prevent Brian from telling his past self about the attacks. They then return to the present, whereupon Stewie learns that Brian has taken credit for the Harry Potter series, and they seek to repair this by again trying to prevent themselves from telling any future events. This causes hundreds of Stewies and Brians to appear, however, to prevent them from telling the future. Having had enough of this, one Stewie tells his numerous future selves to take their respective Brians and return to their time. From there, Stewie takes Brian back a minute before their past selves arrive and forces them to return to their time. With that, the altered timeline ceases to exist along with its corresponding Stewie and Brian.'
this was a amazing time traveling episode!
everything about this episode was great!