Hermux Tantamoq

The Hero: a watchmaker

Amateur Sleuth
Dulcinea Effect: After just one meeting, Hermux is ready to risk his life and reputation to rescue Linka.
Intergenerational Friendship: Hermux and Mirrin. Explained a little in that she was a friend of his parents'.
Must Have Caffeine:
It was one thing to be all alone and facing certain death or worse […] and it was another thing to be expected to do it without coffee.
Nice Guy: He's humble but solid hero.
Renaissance Man: Besides being a watchmaker (and therefore, an engineer, to an extent), he is by turns an amateur archaeologist, a set designer for a stage show, and an Amateur Sleuth.
Shipper on Deck: Mirrin is one for Hermux + Linka. Hermux returns the favor by being one Mirrin + Birch.

Linka

Linka Perflinger

The Love Interest: an adventuress and aviatrix

Ace Pilot: During The Sands of Time we get to see her acutally flying, and landing in tight spaces.
Action Girl: Adventuress and aviatrix
Crazy-Prepared: When organizing her adventures, Linka makes lists of everything, including a list of all the lists.
Distressed Damsel: Linka in the first book, but later on, she proves to be an Action Girl more than capable of looking after herself. She keeps a sharpened ring for escape situations and even kills a scorpion one-to-one.

Mirrin

The Mentor: a blind painter

Blind Seer: Mirrin is a blind painter. She sees visions of cats but is unable to paint them. After she regains her sight, exhibiting the paintings of these cats causes a citywide scandal.
Cool Old Lady
Intergenerational Friendship: Mirrin and Hermux. Explained a little in that she was a friend of his parents'.
Interspecies Romance: Mirrin and Birch. The former is a mouse, the latter a chipmunk. It gets treated more or less like an interracial romance would have been in 1960's America, with Birch being the minority. At one point, when Birch suggests that Mirrin might be happier with someone of her own kind, she tells him, "I've never found anyone of my own kind. Except you."
Shipper on Deck: Mirrin is one for Hermux + Linka. Hermux returns the favor by being one Mirrin + Birch.

Tucka

Hurmux's neighbor, a cosmetics tycoon

Freudian Excuse: Tucka explains away her massive vanity and attention-seeking as a result of being looked down on by her wealthier cousin as a child.
The Heavy: She's never technically a book's Big Bad, but her antics drive the story pretty hard.
Large Ham
Looking for Love in All the Wrong Places: Tucka's lovers all turn out to be bad guys. Justified given how shallow she is; all she looks for are charm, good looks and a willingness to go along with her less than savory schemes.
Platonic Life-Partners: She and Hermux constantly running afoul of each other over a lengthy period of years has forged them into a very dysfunctional and unwilling example of this trope.
Self-Made Woman: Tucka is very proud of being one, as opposed to the heiresses from old families who look down their noses at her. It's one of the few points in her favor, actually.
Screw the Rules, I Have Money!

Terfle

Hermux's pet ladybug

Intellectual Animal: Hermux asks her for advice on more than one occasion. She's also an artist.
New Powers as the Plot Demands: In the beginning, she seems to be an ordinary pet, but by the fourth book, she can draw portraits, design stage sets, give Hermux fashion advice, act as diplomat to a swarm of angry bees, and even get her own point of view narration in some chapters.
Ridiculously Cute Critter: Terfle. How can you not want to cuddle her after reading these books?

Birch

Adventurer Archaeologist: Birch spent decades chipping away at the mystery, but when it all comes into place, it turns into a rapid adventure.
Interspecies Romance: Mirrin and Birch. The former is a mouse, the latter a chipmunk. It gets treated more or less like an interracial romance would have been in 1960's America, with Birch being the minority. At one point, when Birch suggests that Mirrin might be happier with someone of her own kind, she tells him, "I've never found anyone of my own kind. Except you."
New Old Flame: To Mirrin. They met in college, meet again forty years later and they're as deeply in love as ever.
Reports of My Death Were Greatly Exaggerated: Birch never set out to fake his death, but after it happened he realized it could be a good idea, and he went with it.
She Cleans Up Nicely: Birch is a rare male example.

Turfip

Absent-Minded Professor
Derailing Love Interests: He seems like a very nice at first, but later tells Linka to more or less Stay in the Kitchen—that is, to sell her beloved airplane and become the perfect hostess to advance his academic career.
Disposable Fiancé: In the first book, Hermux Did Not Get the Girl because she was engaged. They later break up, and Hermux does end up with her.