  Open Wilson line operators and generalized star product have been studied
extensively in noncommutative gauge theories. We show that they also show up in
noncommutative scalar field theories as universal structures. We first point
out that dipole picture of noncommutative geometry provides an intuitive
argument for robustness of the open Wilson lines and generalized star products
therein. We calculate one-loop effective action of noncommutative scalar field
theory with cubic self-interaction and show explicitly that the generalized
star products arise in the nonplanar part. It is shown that, at low-energy,
large noncommutativity limit, the nonplanar part is expressible solely in terms
of the {\sl scalar} open Wilson line operator and descendants.
