I have that problem with Kat atm. I call out to John in the shops or whatever and she now calls him john. She calls me Ke-ie and if one of us slips and says "thanks honey" or something similar she'll start using honey instead. So cute, but also soooo not what you want your child calling you or ur partner! hehehe
He's called me sexy so she did, he's said I'm grumpy so Kat says "grumpy mummy" and that upsedts me right now cause my hormones are all over the place hehe.
I think it's just a stage. She tells me to shut up because john says that to her when he gets really upset. I try to tell him not to, she's a parrot right now. All we can do is try to model the right behaviour and language and hope they catch on. I tell her when she says something in-appropriate, but being a toddler, she does it more because of this I guess. Oh well, we can only try and continue to love them hey?!