The latest photo trend on Instagram is called Barbie Feet. It's when a picture is taken with a foot or feet extended out as if it were in a high heel. It mimics the perpetual state of the feet of a Barbie doll. The trend has taken off because it makes the subjects in the pictures look taller and have longer legs.
I've seen people (mostly ladies) do this forever! I'm surprised it's a "trend", but I'm never against posing in a way that makes you feel good. Barbie Feet all day, boo.