Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
How many DVD volumes was identified by Skippy Johnson?

### Inputs:
table_name: table, columns: ['Episode title', 'Villain(s)', 'Identity(ies)', 'Reason(s)', 'Original airdate', 'DVD volume']

### Response:
SELECT DVD volume FROM table WHERE Identity(ies) = skippy johnson