*Passionate Lovemaking Ensues*
They wouldn't even notice each other in the room since they were too inwardly focused :P
Nothing. I've seen it too.
Quiet people are normally very observant. The quiet person would probably notice that the painfully shy person is very uncomfortable - what they do then would depend on their personality - let's try it and find out!
one is gonna eat the other one
Try it and find out