Pumbaa's sounder is a group of warthogs whom Pumbaa used to live with. They banished him due to his gas odor, which was apparently appalling even by warthog standards.
The warthogs live in a hut surrounded by a wooden fence. When Timon and Pumbaa arrive after hearing a distress call from them, they see that the hut is surrounded by Guinea fowl. While a pink female warthog named Sharla and three other male warthogs try to figure out a way to survive from the fowl, Timon and Pumbaa fall inside and the warthogs recognize Pumbaa. Pumbaa and Sharla haven't seen each other in years and state that they have never forgotten each other. When they are about to kiss, Timon interrupts and wants to know how Pumbaa knows the warthogs. Pumbaa tells Timon that he used to live with those warthogs years ago they've banished him because of his odor.
When Sharla asks Pumbaa what his plan is to get rid of the Guinea fowl, Pumbaa can't think of an idea and has Timon think of one since he's the "brains of the outfit." When all of Timon's plans don't work, he and Pumbaa go back to the jungle from earlier in the episode to use the battered jeep, which they have to fix first. After Timon and Pumbaa go back to the hut with the jeep and keep the Guinea fowl from coming inside, Sharla asks Pumbaa to be a member of the sounder again, but Pumbaa says he can't and he wants to continue living as an outcast with Timon.
The next morning, the three male warthogs put a big bag of bugs (which later turns out that it actually has firecrackers in them) on the jeep. The bag is used to distract the Guinea fowl and have them leave the colony. Pumbaa says his goodbye to his sounder and he and Timon leave the colony with the jeep and the Guinea fowl chase them for the bag. Pumbaa later reveals that he gave the bag of bugs to his sounder while the bag they had with the firecrackers was to try to fool the birds. Then there is another call from the warthogs, this time representing that their problem is solved.