When size and fit matter, do a gauge swatch. Got that? When size and fit matter,DO A GAUGE SWATCH.
As a new knitter I often thought that was ridiculous and so long as I had a similar yarn (if using a sub) I would be fine. I've smartened up a bit since then and know that isn't always true.
I have pictures today. Luckily size and fit weren't super important. The item is intended for a baby and the difference worked in my favor.
Same pattern, same weight yarn, same needles, and same mods were made. Both are newborn sized.



Pretty amusing huh? So again, when fit is important, do the swatch.
And just as a bonus....the newest FO.




Pics are older and not that great but you get the point. :) Same as the other one but with purple for the body (acrylic again). I love how it turned out...hurt my hands though. And because I know the rules ;) here is a modeled shot (yes I have permission on the photo....baby is much older now).