Related Clues:

• Familiar "Who's there?" reply
• Simple answer to “Who’s there?”
• Possible response to 'Who's there?'
• Common response to “Who’s there?”
• "I'm here!"
• "Here I am!"
• Potential reply to 36-Down
• "I'm home!"
• Words before and after "hi, I'm the problem" in Taylor Swift's "Anti-Hero"
• Announcement made with a knock