Sometimes items can get stuck in your offhand, as the offhand is disabled on survival. Pressing F will open a Keystone menu.
Players have often gotten shields stuck in their offhand, which we can fix by getting a mod+ to grab it for them.
Based on that picture (unless that guy has a weird skin) I believe that is two players inside one another but I’m not really sure how it got in offhand but it isn’t a problem :)