1
general::
Phrase(s): *the teacher’s pet
the teacher’s favorite student. (*Typically: be ~; become ~.) • Sally is the teacher’s pet. She always gets special treatment. • The other students don’t like the teacher’s pet.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
A person who has gained favor with authority, as in Al has managed to be teacher's pet in any job he has held. This expression transfers the original sense of a teacher's favorite pupil to broader use. [1920s]
American Heritage Idioms