"Co-sleeping is dangerous and I'm never going to do it." (Trying to stay awake while feeding the baby at 2am for the 9th time since trying to go to bed? Ahhh no.)
"Baby sling? Pfft that's just some weird hippie thing." (I own two slings and a Manduca).
"No baby of mine will be eating that commercial crap out of a jar." (Making dinner for everyone including baby when I've been awake for 38 hours straight? Yeah right.)
"My kid won't even know what McDonald's is until he's at least 5." (See above.)
"I won't be breastfeeding past a year." (Cried when my little boy self-weaned at 16 months).
"Rear-facing a toddler? That's just ridiculous." (Bought a new seat when I realised my son wasn't even going to make it to 1 RF in the one we had).
Many of these were things I said before I was even seriously thinking about having kids. Most of them changed when I was pregnant and had actually started doing some research. A couple were a very harsh reality check once I actually had my baby