Episodes Suggesting A Conflict
Box and Lightbulb have interacted over the course of the series, since they have been placed on opposite teams in Season 2.
In Breaking The Ice she kicks Box off the ice with no sign of regret, however she did talk to him before doing so.
Episodes Suggesting A Friendship
In Breaking The Ice, Lightbulb shows interest upon seeing Box not interacting with anyone or anything, and asks how he does it. After hearing no answer, Lightbulb calls him "a true master".