In the anime, Mayu, after witnessing Lucy and Nana's first fight, convinced herself that she'd been dreaming, because Nyu couldn't possibly have done something so vicious as quadruple amputate Nana. She later meets Nana, who has gotten prosthetics, and is initially surprised when she sees that her limbs are back, before reminding herself that limbs don't fall off and reattach. Guess what happens next.
When Kouta's efforts to dress the childlike Nyu end with him pulling off her clothes just as Yuka walks in.
When Yuka's efforts to remove her passion-stained panties end with her slipping and showing a flustered Kouta...everything.
When Nana goes to help Bando up, only to have the grip from his artificial arm tear off her own, sending them both flying.
Episode 10.5 has quite a few funny moments involving Nana:
While trying to help Mayu cook, Nana ends up burning the contents of a frying pan, and then tries to cut cabbage, swinging with such force that her prosthetic arm comes flying off with the cleaver still in hand, nearly impaling Mayu in the process. The look on Mayu's face is priceless.
When asked to help Nyu clean up the house, Nana takes it as a competition, running across the floor with a rag so fast that, when she reaches a step, she goes flying down the hallway and hitting the floor with such force that her right arm and left leg are knocked clean off. Nyu calmly picks up Nana's leg... but as Nana reattaches her arm and crawls towards her in a very Kayako Saeki-esque manner, Nyu gets visibly flustered, and when Nana looks up, her nose bleeding heavily, and demands her leg back, Nyu promptly hands the leg over before running away screaming.
When Arakawa tries to stop Kouta, Yuka and Nyu from fleeing, and grabs Nyu 'hostage'. After she gives a speech on the danger of horned girls, she is made to realize who she is holding, and freaks badly.
When amoral scientist Nousou tries to demonstrate his control over the clones of Mariko, only to have his candy stolen.
Kouta comes down with a fever. Seeing as she's the only one at home with him, he decides to ask Nyuu to get him some water.
Nyuu (puzzled): "Nyuu?"
Kouta: "Wa-ter. Wa-ter."
Nyuu (determined): "Nyuu!" * runs off; sounds of her turning the house upside down*
In the final manga chapter, when the ladies are repairing Maple House, and Mayu watches Nana's arm fall off the roof, hammer still in hand.
Also in the final manga chapter, when it turns out the all-knowing Anna was just a shell to make Anna a living computer, and the human Anna emerges from it asks the Agent to ask her a math question, only to realize...
Anna "I don't know! Yes! Everything's back to normal!"
Mayu's "Living Money" lie, that she told to Nana to see if she knew about money. Nana's reaction is hilarious.
Nana's nightmare involving this: As punishment for burning money she gets crucifiednaked.
Right after Nyu essentially tries to molest Nozomi and is caught by Kouta. Her reaction and the joke she wants to play on him. Nana's reaction when she pops out makes the cuteness go away though
One of the omakes for volume 8, when everyone gets drunk. Yuka is specifically bad, moaning about how she is always ruining her panties and crying to the "God of Panties". Nyu all of a sudden is naked and asks Kouta to fondle her, making her rather aroused. Yuka being Yuka gets jealous and.. Starts fondling Nyu. Next page and we cut to Nyu, or really Lucy looking noticeably pissed.
When Mayu first meets Bandou, he realizes she's responsible for saving his life. Since he doesn't like to be in anyone's debt, he gives her his phone number, telling her to call him if she's ever in trouble. A few minutes later he's realized she might know something about Lucy, and is prepared to beat her to get the information... at which point Mayu holds up his phone number and says "I'm in trouble, please help me!" Bandou doesn't really know what to say to that, and lets her go.
After spending a pretty long time as Nyu, when Lucy wakes up, she immediately looks at Yuka, and wonders why she feels a sudden urge to grope her.