Underw-air

This happened a couple of weeks ago, but I just found the napkin I'd written it down on.  One night as Peter was putting Silas to bed, Silas said, "Dad, I need to tell you something."

Peter: "What Silas?"

Silas: "Dad, I think I might be wearing air instead of underwear."

Peter: (Not sure he heard correctly) "What?"

Silas: "After I went to the bathroom earlier, I couldn't find my underwear.  Then I saw some air and I kind of thought it looked like my underwear, so I put it on."

Peter: "So, you're not wearing any underwear?"

Silas: "I think I'm wearing underwear...(pause)"

Peter: "Silas?"

Silas: "Actually, I'm not wearing any underwear."