Hmm, Alex has undergone quite a few subtle changes from the first time of drawing him to the present. Partially because his original design was made... like 10-12 years ago? He started out as just an "anime" version of myself to use as an online avatar/persona and in fan fiction lol. I believe the very first instance of the character was this Digimon fan comic I made back in middle school:
That's honestly the only reason he has goggles LOL because he started out as a Digimon main character, so of course 

This was one of my many comic projects that only got like 5-ish pages in though lol. Some years later, in Highschool, I started drawing the character again with an updated design, along with updated designs for some of my other friend-characters for standalone illustrations, like such:
The main changes at this point were taking the original t-shirt (that was based on one of my favorites from middle school LOL) and stylizing it further, making the lizard design a lot bigger; Adding a jacket, again similar to one I wore a lot, doing those awful half-pants/half-shorts things, and just more detail, as my style had progressed a lot xD
Then I put these characters (and most of my drawing, in general) away for a long time during college. After college I started working on a re-reboot of my comic series that I had been working on since middle school right after the Digimon one, which was one of those "100 chapter shonen inspired mega ultra awesome stories".
Then I got introduced to Tapas and realized through the wisdom of all of the fantastic people here that I didn't want to chain myself to something that impossibly long for a first "real" project lol. So I started writing TreasureHUNT!! as a one shot to ease myself in. Everything about this comic was intended to just be a warm up lap, so I didn't spend too much time during any part of the planning phase because I just wanted to get into the production part... so when filling out the story with characters, I decided to just revisit several OCs that I had from earlier in my life instead of trying to come up with new ones lmaooo. In particular, I didn't want to just reuse the OCs from my other long story in case I revisit it someday, so I grabbed my friend-OCs since they weren't affiliated with any story yet. Anyways, my first updated sketch of Alex from that planning phase is here:
For this jump, I was wanting to keep the essence of the design, but dial it back some since the previous version was very over designed xD Kept the sweatshirt main design, but removed the lizard and arm swirls, turned the pants into just regular shorts, and gave him real shoes.
The last major jump to how he ended up looking for the comic-proper actually came by accident in the storyboarding process. I was going super fast and rough, so a lot of the early panel sketches had him looking kind of like this:

But at one point I accidentally made his little top of head curl a little bigger and more pronounced:

and thought it looked kind of cool so I rolled with it through the rest of the storyboard:
and then that translated into his present appearance:


Not gonna lie though... after working on the comic for almost a year now, I really hate how doofy the top part of his hair looks
One of the things I'm looking the most forward to as I'm coming into the end of the first season is being able to redesign him a bit for season 2 LOL But yeah looking back, he's come a looooong ways~