What is the boy and the girl doing? vs What are the boy and the girl doing?

Some examples from the web:

• The boy and the girl both...
• There's no way the boy and the girl did this alone.
• The boy and the girl are gone.
• The boys and the girls that we met with Rosa.
• There's no way the boy and the girl did this alone.
• Let the boy and the girl come out.
• They'd let her have them back, the boy and the girl.
• And I was privileged because I was born into a family, my father would always encourage the boys and the girls.
• And now the boys and the girls get them.
• The beach loved the boy and the girl, though it had no way of telling them.
• As the boy and the girl ran out from their station wagon, the beach was happy.
• The boy and the girl meet and... and they dance, and they dance...
• The boy and the girl meet.
• And here, the boy and the girl, if a middle-aged mysterious stranger can indeed be called a boy, meet.
• There's no way the boy and the girl did this alone.
• All of the boys and the girls here, in Paris
• And what is the girl doing now?
• If the boy and the girl are both in agreement then I'm in agreement, too
• All of the boys and the girls here, in Paris
• Then, without warning, their lives will be snuffed out and the girls deliver Rob just in time for me to plan the boy's 18th birthday.

Some examples from the web:

• The boy and the girl both...
• There's no way the boy and the girl did this alone.
• The boy and the girl are gone.
• The boys and the girls that we met with Rosa.
• There's no way the boy and the girl did this alone.
• Let the boy and the girl come out.
• They'd let her have them back, the boy and the girl.
• And I was privileged because I was born into a family, my father would always encourage the boys and the girls.
• And now the boys and the girls get them.
• The beach loved the boy and the girl, though it had no way of telling them.
• As the boy and the girl ran out from their station wagon, the beach was happy.
• The boy and the girl meet and... and they dance, and they dance...
• The boy and the girl meet.
• And here, the boy and the girl, if a middle-aged mysterious stranger can indeed be called a boy, meet.
• There's no way the boy and the girl did this alone.
• All of the boys and the girls here, in Paris
• Why - why are the boys out here and the girls in there?
• how are the boys and lauren?
• If the boy and the girl are both in agreement then I'm in agreement, too
• All of the boys and the girls here, in Paris