Well as it turns out, if you knit them, they grow!
(it is not wise to take finished object pictures at night. These colors are crazy different! True to life is probably the progress photo at the top of the post.)
It only took a couple of days of actually knitting on my Wonderful Wallaby to finish it! I picked it up just above the underarms on Saturday night, and grafted together the top of the hood and wove in the ends on Tuesday night! I used a discontinued yarn that I got in a Ravelry de-stash. It's a DK weight, whereas the pattern calls for worsted. I knit the 4T size knowing that would affect the finished size. It came out more like a 3T, but that's ok because the recipient is only 2.
Now, if you've knit the Wallaby before, you might notice that I made a mistake on the placket at the neckline.
I read the directions quickly, and where the directions told me to purl the center stitches every other row, I decided to just not read that and overachieve and purl every row. Once I started doing the garter stitch on the edge of the hood, I realized that I SHOULD have been doing garter stitch all the way down the neckline. Whoopsie. I didn't feel like ripping back all that way....so I decided that the rolling of the placket would just help keep the neckline open. Like, uh, a design feature? Plus, it's a toddler sweater, and we all know toddlers hate sweaters anyway.