Caesar was a passenger aboard Ajira Airways Flight 316 from Los Angeles to Guam when it crashed on the Hydra Island. Caesar assumed a semi-leadership role among the small pocket of survivors there, and took an interest into exploring the DHARMA Initiative station on the island. He appeared to be very secretive, as evidenced by his keeping his discovery of a shotgun to himself. Benjamin Linus shot Caesar with the same shotgun, when Caesar would not let "Locke" take a boat to the Main Island.
Before the crash
When checking in for Ajira Airways Flight 316, Caesar stood behind Jack in line. When he overheard Jack telling the man at the counter about his dead friend, he offered his condolences. Jack, confused, thanked him.
Later, Caesar sat in first class, surrounded mostly by people who had already visited the Island. When the turbulence began to shake the plane, Caesar was shocked and confused, especially when warned by Hurley to buckle his seatbelt. ("316") During the white flash that ensued, Caesar turned to find Hurley had disappeared, and later recounted that other people had witnessed people disappear in exactly the same way before the crash.
The plane crash-landed on the runway on Hydra Island; the pilot managed to place it reasonably safely, but not without the passengers suffering a few injuries. ("The Life and Death of Jeremy Bentham") Caesar later woke up an unconscious Ilana and informed her that the plane had crashed but they were okay. He helped her up and they headed for the beach. ("Namaste")
On Hydra Island
2007 (Season 5)
With the plane crash-landing on the runway, the survivors went to the beach. Frank attempted to gather up all the passengers and crew to explain their predicament and tell them that the best thing is to stay put. However, Caesar rejected this and insisted that they search the "animal cages" and "buildings" he saw when crashing. ("Namaste")
Sometime later, Caesar and Ilana discovered the abandoned Hydra station. Neither of them appeared to have any previous knowledge of the DHARMA Initiative. Caesar explored an office and examined animal skulls and other biological items, books, maps, and charts. Caesar found some of Danielle's maps of the Island, a diagram from Daniel's journal concerning the difficulties of time travel, and a 1954 issue of Life magazine about hydrogen bomb testing. He took a torch and found a sawed-off double barreled shotgun under Ben's old desk, which he stowed away in his bag. Ilana arrived, apparently already having visited the station, and informed him of a man in a suit that Roxanne had discovered whilst scouting south.
Caesar theorized that he may have been one of the passengers who disappeared whilst crashing, but Ilana disputed this, informing him that the man wasn't on the plane. Caesar approached him, and asked his name, to which he replied "John Locke."
Locke, the following evening, approached Caesar at the Hydra, in order to inquire about the passenger list of the plane. Locke explained briefly the DHARMA Initiative symbol on the documents Caesar was reading, and that they had been conducting experiments there. Caesar asked him how he knew that, and Locke replied that he had spent over a hundred days on this island.
When Locke said he could provide answers if reunited with his friends, Caesar informed Locke there were some passengers injured in the crash being kept in a room. He took Locke to a makeshift sickbay in the Hydra, where they were keeping the injured, and when Locke found Ben, he told Caesar that Ben was the man who had killed him. ("The Life and Death of Jeremy Bentham")
Three days after crashing on the Island, Caesar was told by Ben that Locke might already have been on the Island and was a dangerous man. When Locke and Ben were preparing the boat to go to the main island, Caesar interfered and was at the point of pulling out the shotgun to threaten Locke. Just as he discovered that the shotgun was no longer in his possession, Ben pulled it out of his own bag, revealing that he had stolen it, and shot Caesar square in the chest, killing him. Ben then tossed the shotgun to Locke, as an "apology" for killing "him." ("Dead Is Dead")
- Out of all the main characters, Caesar only met Jack, Ben, Hurley, Ilana, Lapidus, and the Man in Black, who was posing as Locke.
- Although Caesar's name was not explicitly stated in "316", it was revealed in the credits as well as the ABC press release. He later was called "Caesar" by Ilana in "The Life and Death of Jeremy Bentham".
- Caesar, along with Ilana, were already mentioned in the fifth Dharma Special Access e-mail. He and Ilana were also hinted at in other videos and mentioned heavily before the fifth season premiere. Despite all this hype, Caesar abruptly died midway into his fourth episode.
- Caesar became the de facto leader of the Ajira 316 survivors, however he was quickly killed and Ilana took control of the group. This is similar to the fate planned for Jack and Kate in "Pilot, Part 1" before the writers changed their minds.
- In the casting call Caesar was described as "a dangerous, physical, and extremely intelligent male between the ages of 35 and 45. Although his intentions are unclear, this much is certain: he's as skillful at charming people as he is at killing them. He also has a dark past..." 
- Taghmaoui was originally intended to be a series regular for Season 5 before being toned down to a guest star. Subsequently, he was also going to become a regular for Season 6, where he was supposed to have a big role (which was taken over partly by Zoe) and also have a large part in the series finale, but he declined because of other commitments.
- Caesar's first appearance was originally meant to be in "Because You Left" but the footage was moved to the opening sequence of "The Life and Death of Jeremy Bentham" 
- Witnesses of death: Benjamin Linus, The Man in Black, Three Ajira survivor
- Last words: "You're not taking anything."
- For fan theories about these unanswered questions, see: Caesar/Theories
- Why was he traveling to Guam?
- Why did he feel the need to hide the shotgun from Ilana?
- Was he another one of Jacob's bodyguards?
- What was his ultimate purpose?