Question: Stellan Skarsgård's son was in what History Channel series?
Context: William "Bootstrap Bill" Turner Sr. is a fictional pirate in Disney's "Pirates of the Caribbean" film series.  Although he is only mentioned in the first film, he appears in the first two sequels, portrayed by Stellan Skarsgård. River is a six-part British television drama series, created and written by Abi Morgan and starring Stellan Skarsgård and Nicola Walker.  It premiered on BBC One on 13 October 2015 and internationally on Netflix on 18 November 2015. Helen of Troy is a 2003 television miniseries based upon Homer's story of the Trojan War, as recounted in the epic poem, "Iliad".  This TV miniseries also shares the name with a 1956 movie starring Stanley Baker.  It stars Sienna Guillory as Helen, Matthew Marsden as Paris, Rufus Sewell as Agamemnon, James Callis as Menelaus, John Rhys-Davies as Priam, Maryam d'Abo as Hecuba, as well as Stellan Skarsgård as Theseus.  The series was entirely shot on location in the islands of Malta. Submission (Swedish: Underkastelsen) is a 2010 Swedish documentary film directed by Stefan Jarl and narrated by Stellan Skarsgård.  In the film, director Jarl has his blood drawn for a series of tests to show how much of a "chemical burden" is in his body. Varela was born and grew up in Södermalm on the south side of Stockholm.  Both parents are from Spain and he did not learn proper Swedish until he started school.  During middle school a new friend was Gustaf Skarsgård, son of internationally noted Swedish actor Stellan Skarsgård.  Varela did not then know of the famous Skarsgård family because he mostly watched Spanish satellite television.  When his friend Skarsgård applied to a selective upper secondary school, Södra Latin’s drama program near where both boys lived, Varela wanted to do the same.  The elder Skarsgård gave the young Varela a few hours of acting instructions and he was accepted by the school.  Varela said he was surprised, because he had shown up in a track suit and looked more like a homeboy/chav than an aspiring actor. Moomins and the Comet Chase is a 2010 3D stop motion animated fantasy adventure comedy family film compiled from the "Comet in Moominland"-based episodes of the 1977–1982 "The Moomins" TV series animated at Se-ma-for in Poland, restored and re-soundtracked with multiple voice actors replacing the single narrator.  It is the second such Moomin film produced by Finnish children's film company Filmkompaniet, the first being "Moomin and Midsummer Madness", and the first one converted to stereoscopic 3-D.  A similar revision of the remainder of the series for high-definition television of all 78 episodes will follow and is currently in production.  The same novel has been adapted into film at least twice before, with the 1978 Russian stop motion serial "Mumi-troll" and the 1992 Japanese traditional animation feature "Comet in Moominland".  The international version of the film features the voices of known Swedish actors like Stellan Skarsgård, Peter Stormare, Alexander Skarsgård.  Musician and Moomins fan Björk also wrote an original song for the film.  The international film debuted at the Cannes Film Festival in May 2010.  In Finland, it arrived in movie theaters on 6 August 2010 and was later broadcast on the MTV3 channel.  The film was also produced in dozens of other languages and subsequently received global distribution. Beowulf & Grendel is a 2005 film Canadian-Icelandic fantasy adventure film directed by Sturla Gunnarsson, loosely based on the Anglo-Saxon epic poem "Beowulf".  It stars Gerard Butler as Beowulf, Stellan Skarsgård as Hrothgar, Ingvar Eggert Sigurðsson as Grendel and Sarah Polley as the witch Selma.  The screenplay was written by Andrew Rai Berzins.  The soundtrack was composed by Hilmar Örn Hilmarsson.  While some of the film remains true to the original poem, other plot elements deviate from the original poem: three new characters, Grendel's father, the witch Selma, and Grendel's son are introduced, and several related plot points were developed specifically for the film. Gustaf Caspar Orm Skarsgård (] ; born 12 November 1980) is a Swedish actor.  He is best known outside Scandinavia for his role as Floki in the History Channel series "Vikings" as well as for his roles in the films "Evil" (2003), "The Way Back" (2010) and "Kon-Tiki" (2012). Steven M. Gillon is the resident historian of The History Channel and professor of Modern U.S. History at The University of Oklahoma.  He received his Ph.D from Brown University.  He has written numerous books and articles on modern American politics and culture.  From 1998-2006, he anchored the History Channel's Sunday morning current events program "HistoryCENTER".  In 2006-07 he hosted the History Channel series "Our Generation". Erik Selvig is a character portrayed by Stellan Skarsgård in the films of the Marvel Cinematic Universe (MCU).  An astrophysicist who becomes involved with the alien Thor and the government organization S.H.I.E.L.D., he first appeared in the 2011 film "Thor".  Skarsgård went on to reprise the role in "The Avengers" (2012), "" (2013), and "" (2015).  To tie into these appearances, the character is seen in several MCU tie-in comics.  The character also appears in other media, including non-MCU comics published by Marvel Comics.
Answer: "Vikings"