乐而忘返的英文是「enjoy oneself so much that one doesn 't want to come back」
le er wang fan
非常快乐,竟忘记回家。形容沉迷于某种场合,舍不得离开。
《史记·秦本纪》第五卷:“造父以善御幸于周缪王……西巡狩,乐而忘归。”