The last three seasons of Game of Thrones have been so blessed Joffrey-free, it's easy to forget that evil child existed in the first place. But exist Joffrey Baratheon did, as well as die. But I assume you've done your best to block this tiny sociopath from your memory the way I have, so here's a quick refresher on who Joffrey was and how Joffrey died on Game of Thrones.
1. He's the reason Arya lost Nymeria.
Back in Season 1, Nymeria protected Arya from Joffrey by attacking him. Joffrey lies about the incident and says he was attacked on provoked and calls for the death of Nymeria. Arya is forced to have Nymeria run away — and Joffrey kills Sansa's direwolf instead. Apart from just being a d*ck move that is indicative of his d*ckishness, this information may be important to remember now that Nymeria returned in last week's episode.
2. He was engaged to both Sansa Stark and Margaery Tyrell.
You probably remember this at least, but it's good to keep in mind how well these two women both knew him — especially considering Sansa's comment to Jon Snow in the Season 7 premiere.
3. He died of asphyxiation from a poisoned goblet of wine.
At a long and tense wedding reception for Joffrey and Margaery (who finally got married), Joffrey spends most of the evening tormenting his uncle Tyrion. At one point, while Joffrey is eating his wedding pie, he orders Tyrion to bring him his wine. Tyrion does, Joffrey drinks, and then starts choking and vomiting and bleeding from his nose. Joffrey dies in his mother Cersei's arms, and his last act is to point an accusing finger at Tyrion.
4. It wasn't Tyrion who poisoned Joffrey.
Though Cersei immediately accuses Tyrion for murdering her son, and though Tyrion gets arrested for it, he was not actually the one who poisoned Joffrey. Nope, it was matriarch Olenna Tyrell who did the deed, in order to protect her granddaughter Margaery from Joffrey's abusive nature. She had some help from Petyr Baelish and Dontos Hollard, who gave her the poison.
5. He never controlled all seven kingdoms.
Though Joffrey did sit on the Iron Throne for quite a while, he did not ever rule all seven kingdoms. Shortly after the Red Wedding in Season 3 and 4, he did have control over the North and Riverlands, but Stannis always denied Joffrey's rule in Dragonstone, and Joffrey never had any control over the Iron Islands. So a true king or queen of the seven kingdoms is still to come — perhaps someone with dragons?