Database: movies_4
Question: What is the most common keyword among all the movies released in 2006?
SQL: SELECT T3.keyword_name FROM movie AS T1 INNER JOIN movie_keywords AS T2 ON T1.movie_id = T2.movie_id INNER JOIN keyword AS T3 ON T2.keyword_id = T3.keyword_id WHERE T1.release_date LIKE '2006%' GROUP BY T3.keyword_name ORDER BY COUNT(T3.keyword_name) DESC LIMIT 1