The robot can be fashioned to look like an actual person, and can converse with people in pre-recorded snippets. When it detects someone nearby, it greets the person and responds to questions.
The possibilities for pranks are endless. If I ever get married, I plan to have one of these whisper "Help me please. I'm the real bride. The robot took my soul and switched places with me. You. Must. Stop. Her." [Japan Probe]