Fred and Betty: Is this the End?

Episode 3: How Betty Knows

Betty: I know all about your other lady Fred! Your friend Martin told on you!

TELL ON

Meaning: if you tell on somebody, you give information about someone, usually about something bad that they have said or done, to a person in authority (like a teacher, boss or parent), knowing that this will probably result in punishment.
小编:tell on sb 这个短语的意思就是”告发,打…的小报告，告…的状”. 我们来看一个简单的例句。
Promise not to tell on me!
答应我，别告发我！

Grammar: This phrasal verb must have an object. You can not separate the verb from its particle.
He told on his sister - RIGHT
He told on her - RIGHT

He told her on - WRONG
He told his sister on - WRONG

更多例句:
When I was a child I used to steal apples from the tree in the neighbour's garden but my brother told on me and my father grounded me for a month.
实战同义词
Synonyms: inform (on), grass (on), sneak (on)

inform on sb: to give information to the police or sb in authority about the illegal activities of sb 告发，检举
He informed on his own brother.
他告发了自己的亲弟弟。

Grass on sb: to tell the police about sb's criminal activities (向警方)告密，告发

Sneak on sb: (儿童向成人)打小报告，告状
Did you sneak on me to the teacher?
你有没有向老师告我的状？