What is the sentence of pulling your leg in idioms?

The sentence would simply be something like "He's pulling your leg" or "You're pulling my leg." To "pull my leg" is to tell me a lie, usually in fun. Suspicious of any lie, we may say "Pull the other one - it's got bells on."

The idiom 'pulling your leg' or 'pulling my leg' means that you're trying to fool me, or what you're saying is a bit beyond belief.