Image from the Mister Donut Japan site. The commercials feature a chubby man in drag. He might be a sumo wrestler, but I'm too far removed from the sport after so many years to be sure.
What is more unfortunate is the fact that there are several possible translations of "pon". It can be the sound that is made when something is hit, such as a ball hitting a tennis racket. It can refer to a mahjongg term or the old video game "pong" by Atari. It can also refer to Pom juice, since "m" and "n" can sound the same in Japanese (hey, don't take me to task for this if you don't like it - I got this from the Japanese Wikipedia page - go bitch at them). It can refer to a type of punch or cereal. It also, apparently, means "small" in the language of the Ainu, the aboriginal people of Japan.
From top left (clockwise): "Nama" (fresh) ring, golden chocolate, nama chocolate, chocolate crunch
So, after all of this research, what did I learn about the meaning of "pon"? Well, I didn't learn anything conclusive, but logic tells me it refers to small round shaped food or food made up of small round shapes. For 10 years, Mister Donut has been making a "pon de ring", which is a rather chewy ring made up of little round blobs (due to being made with rice flour or mochiko). As part of their anniversary celebration, they're releasing a "nama" (fresh) line and a line of mini "pon". The minis look like regular donuts, but are made with the same chewy batter.
Image from Pizza Hut Japan's web site.
I did experience "pon" in other food avenues as well. MOS Burger at one point offered a "cheese pon", which was a super chewy ball of dough with, unsurprisingly, cheese inside. In that vein, Pizza Hut Japan is offering two types of "pon" with rather different flavor profiles. You can see by the little dough blobs flying around the happy fellow's head that they are either stuffed with orange and white stuff or brown stuff. That's cheese filled or chocolate filled. And the common denominator continues to be the chewy texture of these dough blobs.
So, though the Japanese Wikipedia never told me so, experience and current offerings would seem to indicate that "pon" is chewy baked blobs made with rice flour. That means that the "winning" definition on Wikipedia is the one that refers to the Portuguese "pont de queijo", or cheese bread. This is a riff on another European bread product, much as many Japanese baked goods are.
If you're interested in celebrating the anniversary of the pon donuts at Mister Donut with a background screen, there are some pretty funky ones currently on offer. I can't directly link, but if you go here, and then click on the button that I've circled in red above, you'll be given two choices of picture designs. I recommend you click the golden lion designs on the right, but if you get off on transvestite sumo wrestlers, feel free to click the image on the left. Once you click the general style, some other options will pop up that you can choose from, but you should be able to work it out based on graphics and screen resolution size choices.