What is the ruling concerning the white fluid that sometimes comes out when watching movies or talking to the opposite sex? Does it invalidate Wudu’ or affect ritual purity and prayer?

The fluid referred to by the questioner is pre-seminal fluid (madhi), which is impure (najis) and nullifies ablution (wudu). Therefore, one must clean oneself (istinja) from it and purify any part of the body or clothes it touched. It is obligatory to fear Allah and lower one's gaze from what He has forbidden, and to avoid films that contain forbidden elements. Furthermore, a woman's address to a non-mahram man must be within the bounds of proper etiquette and Sharia conditions.