pull someone's leg
idiomUK /pʊl ˈsʌmwʌnz lɛɡ/
US /pʊl ˈsʌmwʌnz lɛɡ/
To say something untrue as a joke to make someone believe it.
Don't worry, I'm just pulling your leg about the surprise party.
OTHER MEANINGS
2. To playfully deceive someone for fun without meaning harm.
She pulled his leg by pretending his car had been towed.
3. To make a lighthearted remark that is not meant to be taken seriously.
When he said he was moving to the moon, he was clearly pulling my leg.
4. To trick someone into believing something false as a practical joke.
The kids pulled their teacher's leg by saying class was cancelled.