How Does Big Bang Theory’s Jim Parsons Memorize His Lines?

From Movieline:

One, how do you memorize the dialogue because it’s not only intricate but you do it to an extent where it almost seems like you actually know what you’re talking about even though it was written by a team of guys who are probably constantly referencing textbooks –

I’ll tell you. I try to find out what I’m talking about. When I first get the script, sometimes they define things in the script for me.

Literally, like a side bar?

Yep. A lot of the time, I’ll go online. I’m very good friends with Dictionary.com and Wikipedia. And then as far as literally memorizing the words, I’ll have note cards. I do note cards all week. And in longhand, I write out all my lines again and again and again. And on the weekends, I drill them. I walk around with my note cards for each scene and do one scene at a time. And I’ll go to my computer, and I’ll type the whole scene out on my word doc and then I’ll go back and I’ll do the second scene, and I’ll type the whole scene out on a word doc. It’s maddening. I will not lie to you. I literally want to kill myself sometimes.

What happens when a revision occurs and you get new pages? Do they put a whole new word in there like —

Yes, but it’s pretty rare. They’re really good about this. Our scripts come, more than anything I’ve seen or heard about, ready to roll, pretty much from the beginning. Every once in a while, something has to be reworded but normally it’s such a minimal thing that it’s not that bad. Sometimes it’s bad. Most of the time it’s really not.