Factual error: In the beginning, Leonard looks at a copy of John G/Teddy's driver's license. The expiration date is listed as 2-29-01, but of course, 2001 was not a leap year, so there would've only been 28 days in the month. (00:12:45)
Factual error: On the upper right corner of the notes Leonard took about the police report, he wrote down the phone number of a detective (Brian Mezear?). It has 8 digits, intead of the 7 or 10 it should have. (00:57:10)
Answer: The are no alternative endings for this film, all that is on the third disk is the movie played in chronologial order so you can see how things really panned out.