Forbidden Friendship

A character wants, very badly, to be friends with someone specific. But sadly, the rules of family or society look down upon the friendship, and won't allow it.

There's a number of possible reasons for this:
 * Prejudice. Whether it's class differences, racism, or any other difference, an entire group of people is declared "evil" and must be avoided if one is to be socially accepted.


 * Personal vendetta. Sometimes one family hates another, and won't allow their own to hang out with the other family. Not everyone in the family shares that dislike, however, and they might become friends anyway.


 * Safety. Sometimes the society or family has a fear of a specific individual, whether warranted or not. And who wants to see their friend hanging around someone who might kill them?


 * Bad influence. Sometimes the specific individual isn't so much a threat to the character, as to society's value system. Friends who do drugs, get into trouble, and so on, might be disallowed as company for the main character.

Examples

 * Tod is orphaned and a old lady adopts it as a pet. A man who lives nearby is a hunter that just got a puppy he is training to be a hunting dog. The two animals meet each other and form a friendship, in spite of the fact that the man is training the puppy to hunt (among other things) foxes.


 * Hiccup and Toothless form a friendship despite the fact Toothless is a dragon and Hiccup is a viking meant to slay dragons. Their bond eventually leads to the ending of the "war" between vikings and dragons, and the dragons becoming the companions of the vikings, so the friendship doesn't stay forbidden.


 * Kiara and Kovu in The Lion King II: Simba's Pride as her father is king and he's an exile


 * In the first Back to the Future movie, Principal Strickland warns Marty McFly to stay away from Doc Emmett Brown, as Strickland views the doctor as a nutcase. It's most likely due to the bad influence factor mentioned above. Some fan theories however suggest Strickland and Doc may have been friends at one time and perhaps ended their friendship on a sour note.