Top Gun
In Top Gun, we have Kelly McGillis playing Charlie and Tom Cruise playing Maverick. She was telling him that she wants to keep her feelings for him a secret when he interrupts her with a kiss! This sweet moment defined the relationship between the characters, but it was not in the original script.

Top Gun
Supposed To End With A Conversation
The truth is that their conversation was meant to serve as a conclusion of sorts. However, the actor forgot the lines he was supposed to deliver. Instead of starting over, he simply went in for a kiss! In the end, the director liked this more than the original plan. This was the reason it made it to the final edit.

Supposed To End With A Conversation