Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_20967430_4 (directed_by VARCHAR, original_air_date VARCHAR)
### Question:
Who directed the episode that originally aired on March 18, 1988?
### Answer:
SELECT directed_by FROM table_20967430_4 WHERE original_air_date = "March 18, 1988"