I've seen a bunch of references to the Konami code being one of the old school references, but I'm not familiar with it. So what is it? I haven't seen the movie yet, so I don't know what role it plays in it, but I figured it might help to be familiar with since everyone is talking about it.
It's best known for use in Contra, where inputting the code at the home screen would get you lots of lives and continues and such. Konami made the NES port of Contra among others, hence the name. It was originally created for the home port of Gradius (1985), which the code's inventor judged to be too difficult for some players. The code is still being used on modern games today.
I absolutely loved the story and the characters. I was particularly fond of Vanellope, whom I personally think stole the show. I totally wasn't expecting the story to end up going where it did, but thought everything about it completely worked. It was also great seeing so many classic characters from existing video game franchises.
One of the scenes I really liked was the conversation between Ralph and Gene in the empty penthouse.