When I first started designing patterns I often made things using fuzzy mohair type yarn, which I then brushed to make cute, furry creatures, including my Adorable Monsters. Unfortunately, mohair yarns have become a lot less fashionable since then, and you can often only find very lightweight ones, which are no good for making amigurumi at a reasonable size. I did make some Adorable Monsters using normal yarn, but I decided to have another go, and make a little Yeti and Bigfoot.
I still wanted to give their fur a bit of texture, so this time I used Stylecraft Alpaca DK, an acrylic yarn with 20% alpaca in the mix. I find it works well for amigurumi animals as it has a really nice, soft and furry feel to it - I used it for my Alpaca Family and Bracken the Fox.
I made a little Bigfoot, tweaking the pattern slightly to give it a thumb, and I was really happy with the way it looked. I then thought it would be nice to have a larger version, something it would be a bit easier to cuddle. If you want to make a larger version of an amigurumi, there isn't any formula to do it. You just have to work your way through it, with an idea of what you want it to look like, and use trial and error to get it right. And some things don't scale up easily - it took a while to work out how to make the bigger fingers and toes when the popcorn stitches I used were just the right size for the original. I decided to make the big version with proportionally longer legs, but otherwise they're very similar.
So, if you'd like to make yourself a cute monster family, you can get the pattern from Etsy or Ravelry. I think they're cute on their own, but even cuter together.