I don't know who my most popular characters are, but I'll do the two (one from each series) who are there for the entire series:
In Wild Nights, Hot and Crazy Days that character would be Carmen, who is also the main protagonist:
1: Carmen knew from a very early age (12) that he was gay, but he kept it hidden from most people until he was almost 30 years old. He remembers the exact moment that he was sure, and this is featured in the book.
2: Carmen almost "came out" at the age of 25 but was talked out of it by his then-boyfriend, who convinced him to stay closeted by making him fear the worst. Carmen would later figure out that this was done for selfish reasons (this, too, is a part of the story)
3: Carmen was always very tall for his age. He was six feet when he entered middle school and was 6'3 by the time he exited. That is where his height peaked.
4: Due to injuries resulting from a car accident Carmen is now 6'2" tall. He lost an inch in height due to crushed discs in his back.
5: Although Carmen is now proudly and fully "out" he is the least "gay" person you'd ever meet, at least by stereotypical standards. He is a mechanic, a deer hunter, an avid angler, dresses like a slob, hates shopping, and can't stand pop music (his musical tastes are stuck in the 1980's, hair metal in particular). It is a running joke at the auto repair shop that he works at that if somebody came in and was asked to pick the gay person out of all the employees he would be the last picked.
6: Carmen does not drink or do drugs, Although he used to smoke (in the 1980's almost everybody did) he has quit long ago (over 20 years ago). He has been drunk exactly once, has been stoned on weed maybe three or four times, and has never tried any drug "harder" than weed. This is mainly because he does not enjoy being stoned.
7: Carmen is a real person. He is me. Wild Nights, Hot and Crazy Days is a true story.
In Finding Daecon's Way, Daecon would be the MC and the only character to be there from the beginning.
1: Daecon is 25 years old and is very tall (6'5").
2: Daecon was raised as an orphan. His parents were never known. This is a plot point.
3: Daecon's appearance is odd for a human: He has pointed, elf-like ears, mismatched eyes, pure white hair, and pointed canines. But there is a reason for this:
4: Daecon is not human. He is a shapeshifter. He only discovered this yesterday.
5: Not only is he a shapeshifter, but as he soon discovers, he is one of, if not the most powerful shapeshifter to ever have lived.
6: Every piece of magic that Daecon has done so far was either accidental or improvised. He doesn't know how he does stuff, he just does stuff.
7: Daecon has just found out that he will be responsible for the survival of the Shapeshifter species. He is not OK with that.
8: This is more a general story thing than a Daceon thing, but all of the events in the book, from the first page to the last chapter, happen over a span of 48 hours. In other words Daecon went from discovering he was a shapeshifter to being their divine ruler within two days.