It occurred to Christopher that, at one time or another, he has used 18 of 24 Greek letters in his classes. So far.

The progression in the comic is interesting in that when he created his previous guest comic in 2010, he was just finishing middle school. He is now, five years later, in college. At Cornell University. Yes, I'm proud. And I'm extremely happy that when I "kinda/sorta" asked if he'd like to do another comic -- not knowing if it'd be as fun as when he was 14 -- he responded immediately. So quickly that I could use it for Comic #999.

I won't stop bragging about my kids -- although next comic I get to brag about me, if for just one day.