Are the characters in The Crucible stereotypes?
This is an interesting question. You could say that the characters are caricatures, meaning that the most radical components of their identities are exaggerated. For example, Danforth is almost unbelievably stubborn. However, since this play is loosely based on actual events (in 17th century and 20th century America - McCarthyism), it might be wrong to say they are caricatures. That is, it might be going too far to say the character's personality traits are exaggerated if they are based on real people. So, even though they might be caricatures, they are based on stereotyped characters in real history.
As far as stereotypes go, it depends upon perception. Do all ultra-religious people act the way Paris does? Not necessarily. In fact, he represents a stubborn, even corrupt religious figure. If anything, he is a stereotype of that particular kind of religious figure. Is Abigail a stereotype of a troubled teen? In many of these cases, you can make the argument that some, or most, of the characters are based on stereotypes.
In literary study, there are stock characters and these are based on stereotypes in society. Some of these stock characters are broadly defined and it would be easy to match up some characters with a stock character type (which is based on a social stereotype). Paris might be considered a "rake." John is a "tragic hero" because he tries to do the right thing but has one tragic flaw: his affair with Abigail.
To prove a character is a stereotype, you have to show how that character exhibits personality traits of other stereotypes which you'd find in fiction or in real life. Although you can call John or Paris a stereotype, it might be more accurate to say John represents the stereotypical "X" in society or literature.