At "Klassic Komix", talk to the guy in there. He will ask for a complete comic. Give him the comic and he will give you gum.
In the Locker inside the school.
In big nate island, find all the missing comic pieces and then give it to the guy who wants it.
On Big Nate's island
bubble gum
By chewing gum that you get by finding all the pieces to the comic strip.
all you have to do to get a pack of gum is: on Big Nate Island you have to collect all of the big nate comic book pieces.
You have to finish the comic for the guy.
You can get chewing gum after you complete the comic and give it to the guy asking you to complete it
you need to finish the comic give it to the guy an he will give you gum
Chew the bubble gum
He is in big nate
Various types of gum effects (some free) appear in the Poptropica Store. However, chewing gum figures prominently in the quest on Big Nate Island. Costume gum will not work. You need to assemble the missing comic strip pieces to get gum from the Comic Book shop. (see related question)
If I remember correctly, you blow bubble gum in the school.