Alexander Skarsgård was joined, on his “ Saturday Night Live ” hosting debut, by his father. Skarsgård had been stoic about what’s going on in his career: He didn’t mention his new films “Pillion” or “The Moment” in his monologue, during which he mimed playing the sax along with the “SNL” band. Later, in a sketch seeming to play off Stellan Skarsgård ‘s success this year in “Sentimental Value,” Alexander and Chloe Fineman played cast members in Scandinavian drama (titled “Stench of a Family”)