Mila Jansen is the twin sister of Lotte Jansen. She and her sister are two pretty Dutch girls from The Netherlands, who are known for their rich and sexually progressive culture. Mila is distinguishable from Lotte only by her dress, which is blue, while Lotte's is green (later red). Mila and Lotte are both voiced by Nick Kroll and they made their first appearances in "Smooch or Share".
In "Smooch or Share", Mila and Lotte make their first appearances, having just recently transferred to Bridgeton Middle School. When Nick invents the game "Smooch or Share", he is quick to invite them to join, for the sole purpose of kissing them. Mila offers her new friends some salty licorice. She also explains that back in The Netherlands, they had their own version of smooch or scare, which is played with a wheel of gouda cheese. There is no way of telling who it lands on but it's not important because the point of the game is for everybody to kiss everybody and later get a slice of cheese. This is a game that students played in kindergarten.
In the middle of the game, Mila makes out with Andrew and compares it to kissing her uncle. Maurice was happy for Andrew and says that the two girls both smelled like herring and dark bread. When Andrew told Nick that he couldn't jerk off if he paid him to, Mila said that there was nothing wrong with paying a young boy to jerk off.
Mila and Lotte were both surprised by the fact that other people could see The Shame Wizard, as they had previously assumed that they were the only ones who could see him. Mila also adds that in The Netherlands, they called him "Father Shame".