Chubby guinea pig
My example piggies are 5.5" with Red Heart Lisa (DK) and 3mm hook, or 6.5" with Red Heart Soft (worsted) and 3.5mm hook. You could use a thicker worsted yarn or maybe even chunky, and bigger hook, for a full-grown adult guinea pig.
The pattern contains instructions for both one and two-color guinea pigs. It is 6 pages long with many photographs illustrating the process. It is written in English with US crochet terms. Stitches and techniques used:
starting with magic ring, chain, slip stitch, single crochet, single crochet increase, invisible decrease
Using only basic stitches this is an easy amigurumi project if you make a one color piggy, a bit more advanced for the color changes if you choose to make a piggy with white blaze on head.
Finished items made from this pattern are yours to keep or gift away or sell, I only ask you to give me credit as designer in case you decide to sell them.