Farkas

Farkas is a Nord, a Lycanthrope and a high-ranking member of The Companions in Whiterun. Farkas is also a member of The Circle. The Dragonborn can marry Farkas, if they have the Amulet of Mara and have completed the Companions Questline.

Relationships
Farkas is very close to his twin brother, Vilkas, and is known for being the stronger of the two. In Kodlak's Journal, Kodlak states that Farkas is kind-hearted and usually follows along with his brother's views in most situations. He also tends to be kinder in his dealings with others. Vilkas tends to joke about Farkas being the more dim-witted of the two.

As a side note, Farkas seems to be a marriage favorite for many Dovahkiin, which is unsurprising, given his kindness towards the player and others, even going to the point to save him/her.

Work to be done
Like "Aela the Huntress" and "Vilkas", Farkas gives an unlimited amount of work to be done. Even after he rids himself of Lycanthropy through the purity quest, he still gives you work.

Proving Honor
The Dragonborn is trapped within a cage and Farkas is surrounded by Silver Hand members. The Dragonborn watches as Farkas transforms into a werewolf and kills all of the Silver Hands.

Purity
Farkas wishes to rid himself of his curse. The Dragonborn has the option of helping him become normal again.

Blades
Farkas is able to become a Blade.

Inheritance
IF Farkas dies, a courier will come and give you a sum of money and a letter. (After completion of Companion's questline.)

Training Exploit
After completing Glory of the Dead, Farkas can be asked to join as a follower. In his speech text there should be a listing for both training and looking into his inventory. If both are present, Farkas can train the Dragonborn, then his inventory can be opened and the money taken back.

Possible fix - When attempting to retrieve your money back from Farkas, you will be able to take the money back. However once you take the money the option to train with him will no longer be there. Needs Confirmation.

Appearances

 * The Elder Scrolls V: Skyrim

Behind the scenes

 * "Farkas" means wolf in Hungarian. His brother Vilkas' name also means wolf, in Lithuanian.
 * There is a bug/glitch where Farkas will draw his weapon, and talk constantly, as if he was a guard attempting to arrest the player. Waiting or attempting to fast travel while in the same building will cause the error message, "You cannot wait while guards are pursuing." It is possible that Farkas is scripted as a Guard, and will pursue the player until all their crimes are paid for by serving jail time or paying the fines. To get around the fast traveling restriction, go outside of Whiterun and find the carriage by the stables. This will allow the player to go to the capitol of any Hold and escape Farkas. (If the Dragonborn has a Follower, the bug can be fixed by asking Farkas to become a follower. He will say that he cannot, and then go back to his normal routine. Note: This may not always work). Alternatively, Farkas can be killed.
 * His default steel armor is randomized as sometimes he will have the set with pauldrons, while at other times he is without the pauldrons. His boots and gauntlets are also randomized between the two varieties.
 * Farkas has a fear of Frostbite Spiders, as revealed during the Glory of the Dead quest.
 * If Farkas joins the Blades, he might travel back to Jorrvaskrr since he is a Companion.
 * Dropping armor near Farkas will cause him to open dialog with the PC asking if he can have the armor you drop. Even if he has permission to keep the armor, he wont pick it up, it'll stay there, talking to him again will make him ask you for the armor once more. This continues until you tell him he cant keep the armor.

Dragon Seekers bug

 * You may experience this bug after you kill the dragon, nothing will happen and there won't be any new dialogue with him to complete the quest, he'll continue to follow you every where and he's immortal (can't be killed - don't waste your time) and the quest never ends.
 * The fix to this bug is to bring down the console "~" and type : setstage CR14 100. Quest complete and the follower is released.
 * This can prevent you from fast traveling, aside from getting annoying because he keeps starting conversations with you. To get away from him, finish a conversation (hit B), then as he is sheathing his sword quickly pause the game (Start or B) and you are free to travel.

Other bugs

 * There is a bug where after you release Kodlak's soul from Hircine, every time you enter Jorrvaskr in Whiterun. Farkas will start following you, open the dialogue box, and unsheath his weapon. This disrupts talking to people, smithing, and combat. You can enter a building ( other than Jorrvaskr) and he will wait outside, or kill him outside the city. Killing him without any witnesses, will trigger the courier to find you and give you 300 coins as directed by his will. Three coins are given to the Jarl of Whiterun as tax, so you only get 297.
 * Alternatively for the above mentioned bug, you can use the console command 'kill' on him which renders him resting on the ground to regenerate. I've done this right after first speaking to Kodlak for the first quest to begin. I don't know yet how long it lasts, but at least I could get away without him interupting me the whole time. He was still considered essential and therefor didn't die.
 * There is also a similar bug to the one above that does not need the release of Kodlak's soul in order to get. It is possible to not have started the quest and he will still follow you. He willgo inside of buildings, and follow you where ever you go.
 * There is a bug after finishing the Companions quest line, there may not be an option 'I'm looking for work' in the dialogue between the player and Farkas or Vilkas, and there will only be the follower request line available. A player can solve this by taking a few more Radiant Quests from Aela the Huntress. After that Farkas and Vilkas will give out quests again.
 * There is a bug where if you attack the Companions, Farkas will constantly follow you, attack you, and open dialog, even in battle. As of right now there is no fix for this, though you can use the ice form shout against him so that he wont be able to interrupt you for a time. Even defeating him will not stop him from following you.
 * There is a bug where if Farkas is your follower and you use the spell "Clairvoyance," the spell's light will only guide you to Farkas and not to your objective.
 * There is a bug where if Farkas is left in Dustman's Carin for a long period of time, at least a month, upon returning to the area, he will continually engage in conversation with you. This will interrupt combat, he will also follow you anywhere, including prison. Finishing the quest in Dustman's Carin will not fix this.
 * Sometimes Farkas will show up about half-way between Nightgate Inn, and Anga's Mill. He still has the same dialogue options, but will comment that he is "tired of wandering around".