Hitchhiker On Halloween Crab

I found 2 of these on a crab I bought. The guy at the store thinks they're barnacles but they don't look like barnacles? They seem to have 2 antennae and some sort of feeding appendage. I appreciate any help I can get on this.

https://youtu.be/t8Y71IjbNZE
https://youtu.be/JuAGJSjBK9o