I need to get up earlier in the morning, Jargo keeps beating me to the punch on replies to posts. As you see from his post, yes, there was a portly Gungan.
My favorite? Jar Jar Binks of course.
What? Oh, this isn't who is your favorite Gungan to hate? Ooops! Make that Boss Nass then.
In all actuallity, I entered into watching TPM with a strong conviction to hate Jar Jar Binks. And at first I was not disappointed in the least ("Exqueeeezzze me!" Nice dialogue George/Amad). But then I developed a love/hate feeling for Jar Jar, switching at intervals between the two. In the end that nutty Gungan wound up growing on me and I liked him despite himself.
Tarpals was a great example of a Gungan with a reserved personality, not too far in either extreme, one of the big problems when a director (of human actors) unleashes animators and directors therof on part of his film and seems to take no active interest in controlling their efforts (a prime example is the elongated musical number in Jabba's Palace in ROTJ:SE, I would hope that had Lucas been directing a human singer, he would not have driven the camera straight down his throat, as the animators did with Joh Yowzah, a serious breach of quality filmmaking protocol that reduced the sequence to Loony Tunes).
Now that I am off of my soapbox, I will cast my lot with Boss Nass. At first I wondered that he was a Gungan at all, until late in the film when we see his ear-thingies tucked behind his hat-thingie. I like the thought that he is a different species (or perhaps ethnicity) of Gungan than the majority of Utah Gungah. The question of why the others follow his lead is simple enough to answer, as "Boss" he is something like the president or king of his people, of all their varied ethnicity. Perhaps most of the red-brown, scrawny Gungans populate that city (the one most convenient to the battlegrounds as it worked out) while other green and purple skinned types (like Nass and Tarpals, remember, he had different colored skin too, and whiskers) are predominant in other cities that were too remote to have lent their armies to the ground battle. Brian Blessed is one of my all time favorite actors and a large than life character in his own right. I was glad to see that he could be a part of the Star Wars saga, which has always had a fine sampling of British actors and actresses.
Bottom line with the Gungans is that there was not ample time to flesh out their culture and the differences between them. A nice touch would have been to intermingle green and purple skinned Gungans amidst those in the ground battle. This would not have increased the cost or difficulty involved in producing those sequences and would have prevented such confusion as to Tarpals and Nass' origins.