Black Widow: There are two things that make her speak Russian, alcohol and when she gets too much into sex. That's how you've learned the language

Emma Frost: She loves to tease you with naked illusions of herself whenever you're busy just to mess with you. It's even worse when she actually walks up to you naked

Gwenpool: She sometimes browses through magazines or Kamala's fanfiction for ideas to try with you. She even takes notes 

Hela: She sometimes sneaks into Midgard (in a disguise) to buy softer sheets for the bed you share, leashes, or even toys. Ask her about it and you're as good as dead

Rogue (classic): Sometimes when the stress is too much, she'll take a spare ship and ask you to accompany her to the Savage Land for a vacation. It's odd as hell, but it always turns out o be fun, in more than one way 

Rogue (Evolution): While she does enjoy DDLG, she gets flustered easily if you compliment her. She loves it, though

She-Hulk: If an orgasm is too intense, she will change back to Jennifer. This used to be an issue for her before you reassured her that you love both forms of her. Now she pretty much collapses on top of you

Storm: While in bed, she may be affecting the weather and not be aware of it. She has gotten better at controlling that, but the occasional rain may still happen

Wolverine (Laura): Can sometimes pop her claws, though on accident. That's why you keep a first aid kit nearby just in case. Fortunately, it has not been required yet, but she does get embarrassed about it

Captain Carter: If a mission takes place a few hours after you've done something dirty together, she'll try her hardest to hide the hickeys on her neck. Natasha always finds out. My god, the endless teasing