Let's take a look at Jimmy Olsen, by the 10's!
We'll start with Jimmy Olsen 10... and here, Jimmy's assumed the role of Jungle Jimmy! So, given that Jimmy has a tendency for disguises and transformations, we'll have to say this goes in the first category, eh? Oh, and bonus points for a gorilla!
Jimmy Olsen 20... and it's a transformation cover!
Jimmy Olsen 30's cover is one I should've posted last Father's Day, eh? This certainly isn't a disguise or transformation cover... must be a "Superman is teaching Jimmy a lesson" cover!
Jimmy Olsen 40's cover is a two-in-one, if I'm not mistaken... it's a Transformation AND a "Teach Jimmy a Lesson" cover! It's just not readily apparent, that's all.
Jimmy Olsen 50 features a transformation (of sorts)... and we see that Jimmy Olsen should never design his own costumes... Green and Orange?!?!?
I can't really explain anything on this cover... especially the speed lines on Superman, indicating his flight direction has nothing to do with his pose!
Jimmy Olsen 70's cover introduces Silver Kryptonite! I wish I could remember what that was now...
Jimmy Olsen 80, and it's about time we got another transformation cover, eh?
Jimmy Olsen 90 features a transformation cover, and it's also in very, very bad taste!
Jimmy Olsen 100! An issue I've never read, but have heard about in the vaguest of terms!
Jimmy Olsen 110's cover is very retro... many Golden Age comics featured covers like these, that had nothing to do with the interiors!
Jimmy Olsen 120... could this be a "Teach Jimmy a Lesson" cover?
Jimmy Olsen 130... one of the most bizarre covers and stories ever!
Jimmy Olsen 140 is a good collection of stories! I think I've owned this issue a few times!
Jimmy Olsen 150's got a pretty weird cover... and where the heck are the backgrounds?
Backgrounds are also sparse on Jimmy Olsen 160!
Unfortunately, "By the 10's" means none of the Kirby issues are included... and sometime in the very near future, we'll pick up on this again with Superman Family, which took over the numbering from Jimmy Olsen!