Table: tv_episode_4
Columns: season
series
episode_title
original_air_date
nick_prod

Question: What is the series # on airdate September 21, 2002?
SQL: SELECT "series" FROM tv_episode_4 WHERE "original_air_date" = 'September 21, 2002'

Question: what is the series number of the "harry bladder special"?
SQL: SELECT "series" FROM tv_episode_4 WHERE "episode_title" = '"Harry Bladder Special"'