He was a new addition to King Arthur's Knights, and joined him later after he'd recruited Sir Bedevere. Together, they set off to find the Holy Grail given to them by God, and King Arthur leads them away from Camelot because it "is a silly place."
At the French castle, Lancelot is required by Sir Bedevere to slip inside the Trojan rabbit along with Sir Gallahad, and leap out at night killing the French soldiers. However, they fail to get inside the rabbit, to Lancelot's dismay.
The French Taunter throws the giant wooden rabbit at them, crushing the squire.
So King Arthur decides they split up if they can find the Grail separately. King Arthur and Sir Bedevere go one way, Sir Robin and his minstrels go through the dark woods, and Sir Gallahad ends up in the Castle Anthrax. He is seduced by the gorgeous women inside until the twin sister of Zoot, the owner, says the punishment for disobedience is "oral sex" and Sir Gallahad says he could stay much longer. But to his dismay Sir Lancelot runs in accompanied by his guards and tries to take Sir Gallahad away and kill the women. However, Sir Lancelot says the "peril" is "too perilous" and he makes no move. Sir Gallahad says "I bet you're gay," and Sir Lancelot says "No I'm not."
During the Quest, Sir Lancelot is with his squire journeying through the woods when his squire is "killed" by an arrow. However, he is "not quite dead" and in fact he's getting better. Sir Lancelot is shown to be rather dim, because he cannot think of "idiom" but he says he'll rescue the "princess" in the note, only to find that the "princess" is just an effeminate singing prince. Disappointed, Sir Lancelot is about to leave before the prince's father shows up, angry at Sir Lancelot killing all the wedding guests as well as the bride's father, to which Sir Lancelot says "Is he alright?" when he just shoved his sword in his brain. Sir Lancelot says he's from Camelot, impressing the King, who takes him down to the wedding hall. There the King is shocked to learn the bride's father is still alive and getting better, so he ruthlessly kills the man by having his guard stab him. Sir Lancelot is shocked by this, even more shocked when the King gives Sir Lancelot to the bride in marriage - fortunately it's thwarted by the "miraculous" survival of the groom.
Sir Lancelot reunites with King Arthur and the Knights in Lagor and they eat Sir Robin's minstrels who had been annoying everyone with songs of their demise. Then, they meet Tim the Enchanter, who is a pyromaniac. He tells them of the Bridge of Death and the Killer Rabbit, which they only take seriously when it kills Sir Bors. The Knights kill the Rabbit with the Holy Hand Grenade, and Sir Lancelot and the others flee from the Black Beast of "Aaaaaargh" which ate Brother Maynard.
Finally, they get to the exit when the "cartoon peril" is no more because the animator had a heart attack, and they meet the Old Man From Scene 24, who is the Bridge-Keeper of the Bridge of Death. He asks them three questions - For Lancelot, it is a) What is your name b) What is your Quest and c) What is your favourite colour? Sir Lancelot answers them all correctly, and enthuses the Knights into running on and being asked the questions. Sir Lancelot disappears over the bridge. Sir Robin, Sir Gallahad and the Bridge-keeper get answers wrong, and are thrown into the Gorge of Eternal Peril.
However, Sir Lancelot, in a humorous twist, gets arrested by police when going to the other side of the bridge, because he killed a historian earlier in one of his bloodlusts. The police later arrest King Arthur and Sir Bedevere, who had been seeking Sir Lancelot.