ear trumpet
A sneaky butt-kisser who eavesdrops on a conversation and then chimes in like they were part of the plan all along.
My boss was ear trumpeting me and my coworkers during the meeting, then acted like she was the main character.
He was eavesdropping on my text messages and joined the conversation like he was my best friend.
She was listening in on my argument and then said, 'I totally agree with you,' like she was the mediator.