What is the sin incurred by someone who forbids something for which there is no religious text, and what is the required repentance in this case?

Issuing fatwas is a serious matter and a great responsibility. Whoever issues a fatwa without knowledge bears the burden of the sin resulting from their fatwa if it violates Islamic law, for the Prophet, peace and blessings be upon him, said: "Whoever is given a fatwa without knowledge, its sin is upon the one who issued it." Repentance to Allah Almighty is obligatory for issuing a fatwa without knowledge. If the intent of the fatwa is that cartoon films are forbidden due to abandoning or delaying prayer, then this answer is correct. There is no harm in purposeful cartoon films free from Sharia violations, but they become forbidden if they distract from the remembrance of Allah and prayer.