It could be the humorous dialogues or the way people react to things in the store. Maybe there are some crazy or absurd incidents that happen, adding to the fun. Also, the way the story is visually presented with funny expressions and gestures can make it hilarious.
A trip to the store can be funny in a comic when there are funny misunderstandings, strange products, or when the main character has a series of comical mishaps. Sometimes, it's just the contrast between the ordinary setting of the store and the extraordinary events that occur that creates the humor.