Though it is probably mostly for self-preservation since the Ventari threatened him, Rincewind constantly trying to pull Twoflower to safety and then making sure he’s all right after something dangerous happened is kinda sweet.
The luggage’s loyalty and protectiveness towards Twoflower is always worth a smile.
“Dr. Rijinswand” (Rincewind’s other dimensional part) believes Zweiblumen (Twoflower’s dimensional part) is sick and he is so panicked that he runs around the plane trying to find help. From what this troper gathered they hadn’t known each other for a few hours and yet he was that concerned about the tourist. This is possibly Heartwarming in Hindsight due to the Jerkwitha Heartof Gold Rincewind would become.
Rincewind saving a frog who was paddling desperately against a current near the rimfall was also sweet. It does turn out to be the Lady's Secret Test of Character for him, though.
Rincewind and Twoflower seem more to be Vitriolic Best Buds in the film than they are in the book. In fact, in Part 2, Twoflower pretty much takes a spell for Rincewind while wizards are shooting at him and pretty much saves his life.