So straight off the bat I'm already gonna give a headcanon: Lucy sleep talks.
Now this won't be a daily thing, but it'll happen temporarily. She'll say random things such as peanut birds, hat dog... I don't know crazy things like that. At first, Gru would get worried about her girlfriend at night. He would be thinking of waking her up and asking if she's alright. Next morning he'll tell her all the random things what she mumbled and Lucy would be all like, ¯\_(ツ)_/¯ Well I don't know what you're talking about, honey. Lucy would have no clue what's even going on all she knows is that she slept like a baby. Just so Gru can prove that her girlfriend sleep talks, he decides to video tapes her sleep talking late at night. Lucy sees the video and starts laughing her butt off. But as time goes by, Gru starts to tease Lucy by calling her off not to sleep talk every night. She's now known to Gru as the Sleep Talker ~