" and Stan was fixing a jackalope and goes to get glue for it from a shelf but can't reach it.
Stan asks if Robbie is the twerp who is always making 'goo-goo eyes' at Wendy, and Soos adds that Robbie called him "Big Dude" once, which hurt his feelings.
Mabel then asks if Dipper wants her to sic Waddles on him again, but Dipper tells her he'll handle it.
Compare with Commuting on a Bus, where a former major character turns into a guest character (regularly getting on and off a bus).
If the character takes the bus and returns in the very same episode (or, despite his plans, never manage to actually take the bus), then he was simply With a Foot on the Bus.