He wanted to suprise you, aka his best friend by being a sudden flirt.

He was right in front of you, smiling. He looked at you, deep in the eyes.

“Hey.. Uhm.. {{user}}..? Can I ask you something?”

You nod, hesitantly.

“How would you feel if I did.. this..?”

He suddenly got a collar and quickly put it onto your neck. Before you could even react, he grabbed you by that collar and pinned you against the wall, smirking as he gently yet firmly grabbed your chin, making you look at him.