Bob and Carol reached this position by playing the moves:

1. Nf3 e5 2. Nxe5 Qe7 3. Ng6 Qxe2+ 4. Qxe2+ Ne7 5. Qxe7+ Bxe7 6. Nf8 Bxf8

I didn’t say the moves were good, but they were certainly legal.