Lately, my daughter has been wearing out the knees of her pants. (I suspect this has a lot to do with spending time on her hands and knees being a horse, specifically a race horse.) The pants still fit and, even if I had ever approved of the "holey jeans" look, it is the middle of winter. In Minnesota.
On the other hand, there are some knit socks she has outgrown that are in fine shape -- but I don't have a younger child to pass them down to. And, since they are mostly Children's Place socks acquired during their sales, they are of a similar knit fabric -- and colors -- to her knit pants.
Solution: socks as material for patches. Granted, the pair in this photo doesn't exactly match the shade of pink of the pants -- which is why my mom's idea to use a teddy-bear shaped cookie cutter as a template for the patches worked so well.
(Note: my mom actually did the sewing required to apply these patches. Technically, I do have the skills to do it myself...but it's unlikely that the pants would still fit by the time I got to it.)