I'm John - A way to tease someone by acting like them and making fun of

A way to tease someone by acting like them and making fun of how dumb they are, comparing them to the idiotic John.

'I'm John' he said in a fake voice, 'I'm John' he said again, 'I'm John' he said with a face full of sass.

She copied his stupid voice and said, 'I'm John' like she was the king of dumb.

He walked into the room and said, 'I'm John' like he was the most annoying person ever.