An outcast. That seeks social acceptance within a group of close friends that he isn't a part of, by standing outside the circle group. Peaking his head in to eavesdrop on the conversation and when the circle opens up inciting him in, he almost seems scared by the invitation and backs off behind another member of the circle.
To jack (steal) someone elses expression(s). The person who always Jack-spressions is usually too lame to come up with their own expression.
Emily told Leah and Moe that she was crushing on Conan O'brien. Leah squinched her nose and formed and O with her lips. Moe Jack-spression(ed) and repeated the same reaction.