I/he/she wasn't born yesterday!

something that you say in order to tell someone that a person is not stupid and cannot be easily deceived.

You'd better think of a better excuse about the dent in my car. I wasn't born yesterday, you know!

You can't expect your mother to believe that - she wasn't born yesterday!

• a lady-killer
• a lager lout
• a lame duck
• a lard-arse
• alarm bells start to ring
• a last hurrah
• a latchkey child
• a latchkey kid
• a laugh a minute
• a laughing stock
• a laundry list
• a law unto
• a law unto yourself
• albatross around neck
• give the thumbs up
• give the time of day
• give the willies
• give the works
• give to on a plate
• give to on a platter
• give to on a silver platter
• give to someone on a plate
• give to someone on a platter
• give to someone on a silver platter
• give tuppence