Introducing: these are going to be people who stick around for a while, or any character introduced by the kids on the show who is part of the background, i.e. The P*lace’s owner, other store owners

Guest star: Obviously, someone just popping in for that episode

Invention count: only for Riley episodes, this keeps track of how many things Riley has invented or claimed to invent (or possibly didn’t, like MAC)

Vocab: This is words and phrases heard on the show, such as “gweeb”. The number in parentheses indicates how many times a word or phrase has been used.

Continuity, gags and themes: These are the things that happen more than once on the show, things we know for certain about characters and the neighborhood, and repeated plot ideas.

New Locations: For review purposes, “new” locations are the ones that get mentioned or used in the episode.

Pop culture references: Any references to real life musicians, movies, or stars. I’ll try to provide links to official sites, Wikipedia articles, or imdb listings in case you have no clue who these people are.

Solos: I’m counting solos as someone singing all the lead vocals by themselves. The number in parentheses is how many solos each kid had per episode. The last number is how many solos each kid has had up until this point. For instance:
Kid (2) = 16
Kid had two solos in that episode. His total number of solos is now 16.

Episode Total: All solos in that particular episode.

Total: The grand total of all solos in the reviewed episodes.

Performance outfits: These are all the coordinating outfits the kids wear, not only in stage final numbers, but in other musical numbers where there’s a theme to their clothes.

- Any little facts that I’ve noticed that don’t fall into other categories are listed here.

Songs:
The songs are rated on a 5 mic scale as well.

When I come up with new categories, I'll explain those, too.
I hope this helps!