The Heffleys' Pig

Oink The Heffleys' Pig is a baby pig owned by the Heffley Family, first introduced in Diary of a Wimpy Kid: The Long Haul. It seems that he is only fond of Manny, just like how Sweetie is only fond of Susan and Gramma. The pig is the second farm animal won by the Heffleys after a goat (mentioned in Diary of a Wimpy Kid: Cabin Fever) which was won by Greg for correctly guessing a goat's weight, but Frank didn't let them keep it, just like that case, Frank didn't want to keep the pig but Susan says she can't return him because the pig "imprinted" on Manny. Rodrick also agreed to keep the pig as he thought you could get bacon from him every morning the way you get eggs from a chicken.

The Long Haul
The Heffleys won the pig in the Highway 1 Country Fair for guessing the weight of a grown hog correctly. The baby pig was originally going to be returned since Susan Heffley only entered the contest for fun. But the crowd was insulted, and wouldn't take no for an answer, which made her change her mind. The baby pig would eventually "imprint" on Manny.

The pig caused trouble for the Heffleys. They tried to bring him into the the second hotel they stayed at by hiding him in the cooler. While there, he caused a mess in one of the bathrooms, and ate all the food in both of the minibars. Later, while in the van, he woke up and caused chaos, which resulted in Greg Heffley getting bit by the pig. Because of all that Susan put the pig in a petting zoo. Manny was heartbroken by the news, while the Heffleys took Greg to a vet to check Greg's bitten finger. The Heffleys came back for the pig later, when they where aided by two Spanish men. At home, Susan managed to teach him some tricks.

Old School
Greg says that Susan Heffley would reward the pig with a cookie every time he stood on his back legs. Since then, the pig had learned to walk on his back legs and never walks on all four hooves. Greg then talks about how he doesn't wear collars or leashes because he thinks he is too good for them, also pointing out how he didn't know how the pig had managed to do it without thumbs. The pig is able to walk into the open world to the content of it's heart, with the addition that it does not have a curfew, unlike Greg. It is possible that the pig might have learned to write, as Greg seemingly gets a letter from the pig during his trip to Hardscrabble Farms. However, this could have been a prank set by one of the family members.

Personality
The pig is suprisingly smart. He somehow opened three cans of soda, can use the TV remote to watch television with Manny and was able to remove his GPS collar soon after being put on him, despite not having fingers. That makes Greg feel annoyed. The pig also walks on two legs, refuses to wear a leash, and eats at the dinner table. The pig also wears a pair of Manny's shorts which Manny put on him.

Appearances

 * Diary of a Wimpy Kid: The Long Haul (First appearance)
 * Diary of a Wimpy Kid: Old School (Last appearance)

Trivia

 * According to the page 104 of Diary of a Wimpy Kid: The Long Haul, the pig is a male.
 * He is a domesticated pig as he is from a livestock of a farm.
 * The name of the pig is currently unknown, it is also unknown if he has been named or not.
 * He wears shorts as of Diary of a Wimpy Kid: Old School
 * He eats at the dinner table
 * He walks on his back legs because Susan taught him how and doesn't on all four anymore starting from the 10th book.
 * He might be able to write letters as seen on page 172 of Diary of a Wimpy Kid: Old School when Greg talks about his mail, though this is most likely a prank.
 * He doesn't wear leashes or collars because he supposedly thinks he is too good for them. Further more he is capable of taking a leash off of him despite lacking thumbs.
 * Out of all the characters introduced, the pig seems to be the most personified as Pigs cannot learn how to walk on there hind legs, due to obvious bone structure reasons similar to that of dogs (there has only been one pig in the history of the world who currently resides in china who can walk on his front legs) and Pigs cannot write for numerous reasons.
 * He once wore a collar but in about 5 minutes he threw it out
 * The pig appears to be super smart since he walks on 2 feet, can use the tv remote, can remove his gps collar despite not having fingers, thinks he is to good for leashes and wears a pear of Mannys pants given to him from Manny. It is also possible the pig can write as shown on Page 172 of Diary of a Wimpy Kid: Old School. The pig also learned to use the toilet as shown in the book Diary of a Wimpy Kid: The Long Haul when he goes to the bathroom despite no explanation that he's been trained too.
 * His name might be "Junior" according to a twitter post by the series author, Jeff Kinney. He explained that the pigs name might really be named "Junior" in the series spanish translation. The twitter post is here