What is the ruling according to the Malikis on the prayer of the congregants during the Friday prayer if the Imam intentionally laughs in the first rak'ah: do they complete it individually, or do they pray Dhuhr, or do they appoint a successor?

If the Imam laughs intentionally, his prayer and the prayer of those following him become null and void in the Maliki school of thought. In this case, he should not appoint a successor (istikhlaf) because everyone's prayer has become invalid. As for appointing a successor in the Friday prayer, it is obligatory for the congregants if something prevents the Imam from completing the prayer, and it is recommended for the Imam to appoint a successor. If he does not appoint one, the congregants should appoint one as a recommendation. They are permitted to pray individually in prayers other than Friday prayer, whereas in Friday prayer, they must appoint a successor. This differs from the case where everyone's prayer becomes invalid due to loud laughter (qahqaha), where the Imam does not appoint a successor and everyone's prayer becomes invalid, whether it was an individual or congregational prayer.