Is it normal to hear voices in your head when you're half asleep?

last night i was laying in bed, my eyes were open but i was half asleep(i think), and a voice in my head started talking to me, it sounded like my dad. he said ''did you take a pill'' i replied(cause i thought i was REALLY talking to him), i said ''yes. 20 minutes ago'' he said ''did you take it'' i said ''yes. i just said that i did'' he said ''don't ignore me. did you take it. yes or no'' i then got annoyed & said ''oh my god, are you deaf. i said yes! i took a pill 20 minutes ago, geez....'' ..then i woke up completely and was a little confused. i realized that i really wasn't talking to my dad or anyone.. i've heard unknown voices in my head also when i am half asleep.. is that normal? thanks :)