Love Montage

This happens when a new romantic relationship has been formed between two characters in a movie or TV show. There's some sappy pop song playing about love playing in the background as the two go through various scenes expressing their love for each other.

This is so overplayed that there have been many efforts to parody it, even entire movies made for the sole purpose of spitting in the face of the disgustingly overplayed romance UnTrashes. Some of those efforts were very successful.

This might happen when two bad guys get together, fall in "love", and hit the town by doing more evil, this time as a team.