I wanted to show you the difference between a mistake and a variation on a pattern. The sock on the left has a mistake (knit 3 rows, purl 1 row instead of knit 2 rows, purl 2 rows). I didn't see it until after the sock was finished and I was attaching it to it's sock life partner. I can only hope that the toddler who will be wearing this sock will not be shunned by the rest of the toddlers for second rate socks.
The sock on the right has an unintended pattern variation. Note how the second block which should be k2,p2 for 2 rows is k2,p2 for 3 rows. Now you may be asking, "Diane why isn't that a mistake?" A good question. It's not a mistake because I saw it before casting on the sock's life partner and therefore was able to do the same variance on the second sock. Almost like it was a plan.