Zapp was first seen when Leela, Fry, and Bender were sent to gather animals off of an exploding planet. The same planet where they found Nibbler. Leela had always dreamed of meeting Zapp, and came aboard the ship. They had all met Zapp, and he offered to invite them all to dinner. While eating, Zapp heard that Leela and her crew were going to save the animals from that planet. This was violating 'Brannigan's Law.' He had them arrested, and thrown in prison.
He later sent Kif Kroker, his assistant, after Leela. She was to be brought to his captain's quarters so they could have sex. Leela came into the room to try and reason with him about saving the animals, but all he was interested in was her. She felt pity in his stupidity, and slept with him. The next morning, she realized her mistake, and took off running. Zapp, too proud of himself to care, told Kif to "Inform the men. I have made it with a woman." Leela later saved the animals, but ran out of fuel trying to escape the planet. Her only option was to call Zapp for help. Ever since then, every time Zapp sees Leela, he has tried to talk her into a relationship, but ultimately fails.
Zapp appears to be incredibly stupid. He cannot seem to pronounce foreign words, like champagne (sham-pag-en). He even once was late to a ribbon cutting for the new DOOP headquarters, and tried to cut the ribbon long distance with his ship's laser. He turned the power to full, and blasted through the space station, cutting it in half. He was kicked out of DOOP, and was sent to live a homeless life on Earth. While there, he found work as additional crew on the Planet Express ship. Fry and Bender liked Zapp much better than Leela, and mutinied against her on charges of not being able to prevent a mutiny. He later tried to blow up the capitol building of a completely neutral people's planet. In the middle of it, he and Kif escaped, while Leela saved the day.
Although he seems to be stupid, he is an excellent space ship captain and general. He has conquered many planets and has piloted many ships such as the Nimbus, the Planet Express Ship, and a space version of the Titanic. While piloting the Titanic, he changed the course to fly through an asteroid belt. He thought, "Maybe we'll get a gravity boost, or something."
Though he appears to be brave and fearless, he is really quite the coward. When trouble happens, he usually escapes, cowers somewhere, or hides behind others, asking for help or protection.
Zapp lead an army to war that Leela, Fry, and Bender had joined. They were the invading aliens on a planet of ball people. Leela was disguised as a man due to women not being allowed to join the army. Zapp hit on male Leela repeatidly. Zapp was asking "him" to shower with him. Hinting that Zapp might go both ways.