Simple

SELECT * FROM gallery2 WHERE topic_id="1666350" UNION SELECT * FROM gallery2 WHERE topic_id="1616125" UNION SELECT * FROM gallery2 WHERE topic_id="288221" UNION SELECT * FROM gallery2 WHERE topic_id="1599065" UNION SELECT * FROM gallery2 WHERE topic_id="209759" UNION SELECT * FROM gallery2 WHERE topic_id="1005272" UNION SELECT * FROM gallery2 WHERE topic_id="434984" UNION SELECT * FROM gallery2 WHERE topic_id="984495" UNION SELECT * FROM gallery2 WHERE topic_id="346952" UNION SELECT * FROM gallery2 WHERE topic_id="459753" UNION SELECT * FROM gallery2 WHERE topic_id="1405277" UNION SELECT * FROM gallery2 WHERE topic_id="1004343" UNION SELECT * FROM gallery2 WHERE topic_id="1353727" UNION SELECT * FROM gallery2 WHERE topic_id="1773907" UNION SELECT * FROM gallery2 WHERE topic_id="1230189" UNION SELECT * FROM gallery2 WHERE topic_id="1513210"