Fairy Tail is a manga series created by Hiro Mashima and originally published in the Weekly Shōnen Magazine since August 2006. It spawned an anime series that ran between October 2009 and April 2013 with a sequel series to start in April 2014.
The main character is Lucy Heartfilia, a teenage girl who wants to join a mage guild so that she can become a full-fledged mage. When she meets a mage named Natsu and his talking cat sidekick Happy, little is she aware that she is about to become part of one of the most infamous mage guilds in history, Fairy Tail.
Natsu and the Dragon Egg (S01E20)
Natsu flame-grills a giant fish and eats it whole, leaving Happy infuriated.
While Lucy explain how Erza get saved, we can see Natsu with a swollen belly.
Call of the Dragon (S02E20)
Happy has a nightmare about getting fat when Daphne is promoting her new diet food.
Magical Ball (S03E29)
In the episode, Natsu comes to tell Lucy that he has eaten too much from the banquet and appears comically fattened, but realistically bloated the next shot and slim again the shot after.
Tartaros Arc Prologue: Fairies vs. the Underworld (S15E??? E235 of whole series)
About the end of the episode, Natsu ate an explosion saving him and others within a house. When one questions what happene, she is surprised to see that Natsu had a rather large bloated belly.
In a bumper, Happy appears stuffed with fish.
A mage of the Fairy Tail guild, Nab has grown from muscular to plump seven years after the destruction of the Tenrou Island.
A member of Shadow Gear, Droy has also gained weight in the seven-year time skip, but from stress-eating. Ever since, he has obtained a humongous appetite.
A mage of the Mermaid Heel guild, Risley is a user of Gravity Change Magic, which will make her slimmer once it wears off. Her catchphrase in rough translations is "Don't look down on the chubby!" Which she occasionally replaces the word "Chubby" with another word.
A powerful dragon-slayer that can take the form of a dragon. While fighting the heroes, a magic cannon blast is fired at him. He momentarily bloats up.