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, even if he does seem a little... slow.
During the quest Proving Honor, the Dragonborn and Farkas are in a ruin. The Dragonborn is trapped within a cage and Farkas is surrounded by Silver Hand members. To kill them Farkas transforms into a werewolf then opens the cage to free the Dragonborn.
During the quest Glory of the Dead, Farkas accompanies the Dragonborn, along with Vilkas and Aela the Huntress, to Ysgramor's Tomb to remove Kodlak's lycanthropy so he can ascend to Sovngarde. While in the tomb, Farkas' fear of Frostbite Spiders gets the better of him, and leaves the Dragonborn and Aela to finish the quest.
Farkas becomes a potential marriage candidate after the progression of the Companions Quest-line.
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.
Remember that there is still a level 90 cap, as with any trainer, even if that NPC is the highest-level trainer there is for that skill.
Farkas may be recruited into the Blades. If Farkas joins them, he might still travel back to Jorrvaskr.
When in his quarters in Jorrvaskr, against the far wall, there is a lute. This could be considered a reference towards Farkas' voice actor, Michael Popeye Vogelsang, being the lead vocalist and guitarist for the band, Your Favorite Train Wreck.
During the quest, "Proving Honor", if the Dragonborn asks Farkas if the Companions are werewolves, after explaining it, he will say "It is a secret to everyone", a reference to the well-known line from the The Legend of Zelda games.
Farkas' skill with heavy armor is unusually low, despite being able to train the Dragonborn in its use.
Farkas is the only Companion essential even as a follower, and after Glory of The Dead.
Click to see the list of bugs encountered
Dragon Seekers bug
PC 360 PS3 The Dragonborn may experience this bug after the dragon is killed; nothing will happen and there won't be any new dialogue with him to complete the quest. He'll continue to follow the Dragonborn every where and he's immortal (can't be killed - don't waste time) and the quest never ends.
PC Solution: The fix to this bug is to open the console "~" and type setstage CR14 100. Quest should complete and the follower should be released.
360 Solution: 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 the player is free to travel.
360 Solution: If you wait 31 days for the dragon to respawn then you can kill it again. Farkas' regular finishing dialogue for the quest starts once you talk to him and then you are free.
PC 360 PS3 As well as this, during Dragon Seekers, there is a known bug in which there is just a floating cursor away from the area needed to kill a dragon in. However, there is no dragon to be seen, causing Farkas to follow the Dragonborn without normal dialogue options.
PC Solution: Set the quest stage to 20 using the console command "SetStage CR14 20". Normal dialogue options will be restores as if you have killed the Dragon.
360 PS3 Solution: Unfortunately, the only solution is to revert to save prior to taking the quest, or a temporary fix so he does not interrupt dungeons is to use the Ice Form shout on Farkas before entering. This should make him only continue following you when you exit the dungeon.
PC 360 PS3 If the player finishes the Dark Brotherhood contract: kill Anoriath, before accepting the quest from Farkas about intimidating Anoriath, The Companions Guild will become unfinishable due to Anoriath being dead. He will also continue to follow the Dragonborn and attempt to talk to you even if you are in another NPC dialogue option.
PC 360 PS3 After the player releases Kodlak's soul from Hircine, each time Jorrvaskr is entered, Farkas will start following the player, open dialogue, and unsheathe his weapon. This disrupts talking to people, smithing, and combat. Farkas has also been known to behave this way even prior to releasing Kodlak's soul.
PC 360 PS3 Solution: The player can enter a building (other than Jorrvaskr) and he will wait outside, or can kill him outside the city. Killing him without any witnesses, will trigger the courier to find the player and give him/her 300 as directed by his will. Three coins are given to the Jarl of Whiterun as tax, so the player only gets 297. Attempting to use the console to kill him while he is a follower will cause him to crawl along the ground but will not kill him as he is flagged as essential.
PC Using the console to kill him is possible by first removing his essential setting. Opening the console and typing setessential <base_ID> 0 turns it off. After this, typing kill with him selected should work.
PS3 During the quest to free Kodlak's soul, if he is performing this bug, he will say "For Kodlak!" and repeat it until the quest is finished, even if he is in combat.
This glitch may be avoided if the player reloads the save file after Farkas begins to follow the Dragonborn.
PC 360 PS3 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.
PC 360 PS3 Solution: 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.
PC 360 PS3 If the player attacks the Companions, Farkas will constantly follow, attack, and open dialog with the player, even in battle.
PC 360 PS3 Temporary solution: As of right now there is no permanent fix for this, though the Ice Form shout can be used against him so that he won't interrupt for a time. Even defeating him will not stop him from following the player.
PC 360 PS3 If Farkas is a follower and the Dragonborn uses the spell "Clairvoyance," the spell's light will only guide the player to Farkas and not to the objective.
PC 360 PS3 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 the player. This will interrupt combat. He will also follow the player anywhere, including prison. Finishing the quest in Dustman's Cairn will not fix this.
PC 360 PS3 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".
PC 360 PS3 If given the wolf armor, after some time it will turn into his default armor. This may happen since he was intended to wear this as his default armor.
PC 360 PS3 The members of the Companions, including Farkas, have a tendency to act like Skyrim guards, continually pestering the player if there is a bounty placed upon them in any hold.
PC Solution: If the bounty cannot be removed by serving jail time or paying them off, use the console command paycrimegold 0 0 <factionID> which will result in paying the bounty, but without going to jail or having stolen goods removed. Look up the faction ID for each hold, or do them all if unsure of which cities the bounties are.
360 PS3 Solution: 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 capital 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.
PC 360 PS3 Farkas, as a few of the Companions, has a bug where he behaves as if Skjor is still alive, with dialog stating he is. This may or may not be related to the bug where Skjor actually comes back to life, due to essential characters returning after 1 month game time.
PC 360 PS3 If Farkas is still tagged as an essential NPC, he may still pursue you around Whiterun, regardless of his injuries. For instance, if a dremora lord is summoned to kill him, he may be decapitated, resulting in a headless Farkas running around the city. If he is headless, dialogue boxes are open, but not usable.
PC Dropping armor near Farkas will cause him to open the dialog box, asking if he can have the armor that was dropped. Even if he has permission to keep the armor, he won't pick it up; it'll stay there. Talking to him again will make him ask for the armor once more. This continues until he is told he can't keep the armor.
PC 360 PS3 Like his brother, he is also very difficult to recruit into the blades, as he will initiate dialogue with the player anytime the player tries to speak to Delphine, or any other time dialog is finished.
PC 360 PS3 It may be possible to marry Farkas before the end of the companions questline.
PC 360 PS3 Farkas may set any or all armor in his possession as his starting armor, even if it isn't, making it impossible to take it away from him.
PC Solution: Use Console Commands and type removeitem <item ID> <count> after selecting Farkas by either clicking him or using his ID.
PC 360 PS3 After marrying Farkas, his steel armor will be sold in the shop he opens. He may not wear it when he is not a follower.
PC 360 PS3 After purchasing his steel armor, he may not carry anything heavy.
After marrying Farkas and choosing to keep on living at Jorrvaskr, he may vanish during the night. (Confirmed on PS3)
A possible fix is to complete Purity, once he returns to Jorrvaskr, he will hurry to his room.
PS3 In Dustman's Cairn, if the Dragonborn accidentally hit Farkas while killing the draugr in the first room, he will continuously limp around, even at full health. You are unable to activate dialogue with him and he will not help you when you get trapped behind the bars and the Silver Hand come in. Thus said, he will not turn into a werewolf and the Silver Hand will never come. You will be trapped behind the bars forever unless you load from a point previous to him limping around at full health.
If married to him, he may not sleep in any house beside Hjerim, where he will choose the housecarl's bed instead of the one in the master bedroom.
There is a small bug where you can get Farkas as a follower before completing the questline. Drop any kind of armor, and he will ask you Mind if i take that armor?, if the Dragonborn selects Consider it Yours, he will take it and go back to his daily bread-eating. (Glitch:You can not accept a Job from him, due a glitch. He will repeat Mind if i take that amor? all the time. Easiest way is to go to Aela The Huntress and accept the Animal Extermination quest, and kill the wolf in Ysoldas house. (And yes, he will be your follower before completing the quest.)
He will continue to follow the Dragonborn and attempt to talk to you even if you are in another NPC dialogue option.(PS3)
Farkas will marry you if you get him as a follower by dropping the Armor. This is an easy way to get him as your husband before even completing the quest of the Companions.
Upon entering the Riften Warehouse, while working on the Miscellaneous Quest "Recover Skooma Source Information", when trying to talk to him, he will only respond: "You're not supposed to be here." And you can not talk to him other wise. Leaving the warehouse fixes this bug. (Confirmed on 360, not tested in PC or PS3.)