Sven is, like Rose, basically an idiot, who isn't accustomed to modern life very well. Dorothy says he even offered to go out and kill dinner for them the night he arrived.
Blanche and Sven go out to eat one day and Blanche spots one of her boyfriends, Floyd, coming into the restaurant with a girl half his age (and, as Sven points out, half Blanche's age as well). This makes Blanche jealous, so she pretends that Sven is a new boy toy of hers and she starts kissing him and feeding him in front of Floyd.
Blanche did all of this just to make Floyd jealous, but Sven took it seriously, and he finds that he now loves Blanche and wants to take her back to St. Olaf with him. Blanche is conflicted and doesn't know how to not hurt Sven's feelings. They talk things out but things don't really get settled until a sexy young blonde girl from St. Olaf arrives at the girls' house, demanding that Sven return with her. She has been chosen to be his bride. Sven is instantly attracted to her and he quickly gets over Blanche and runs off with the girl, whom Sophia calls "The Lean Mean Swedish Machine." Blanche is very upset over having been dropped by Sven like that, but then Floyd calls her and invites her for a day out sailing and she gets over Sven easily.