I know a guy who pretended he was a Garda as a joke and pulled over a car with a good looking woman driving.
She stopped, he was chatting to her, but her boyfriend pulled up behind in another car. The boyfriend knew he wasn't a Garda.
It ended up as he punched the boyfriend in order to escape, but the real Gardai were right behind and he got nowhere.
He got 18 months.
Wasn't so funny then I bet.