My friend and I were playing MC on 15w40b, and in the log it said gumgum87 joined the game twice. (gumgum87 is my friend). And it actually created another "NPC" of him, showing an alex skin floating up in creative mode. Please help!

The same as the summary.

My friend and I were playing MC on 15w40b, and in the log it said gumgum87 joined the game twice. (gumgum87 is my friend). And it actually created another "NPC" of him, showing an alex skin up in the sky. I freaked out. Please help!