In Gone in a Flash, it is revealed that Kowalski has a crush on a dolphin named Doris, though according to Skipper, she just views him as a friend. ("She just likes you, she doesn't like you like you") and ("Reality check, Kowalski. She's just not into you").
In The Trouble With Jiggles, Skipper said "Anyone whose last name doesn't end in -OWALSKI have any options [to stop the jiggli]?", suggesting that Kowalski is actually Kowalski's surname.
In the Egyptian/Arabic translation, Kowalski's name is "Abcarino". The word "abcari" means 'genius' in Arabic.
Happy King Julien Day! reveals that he loves candy, possibly more so than the other penguins, as he dives into the piñata when it finally breaks open to get at the candy inside.
The episode The Hidden revealed that he has a hard time thinking on his feet. He doesn't "listen to his gut" (i.e. follow his intuition) because he claims it to be physically impossible.
In I Was a Penguin Zombie, when they see Skipper acting crazy due to the side effects of a topical cream, Kowalski and the others believe that Skipper became a zombie. Kowalski assumes command until Skipper manages to pull himself together, but Kowalski tricks Skipper into believing him. In the end, Kowalski, Rico, and Private try to catch him, but they end up breaking their wings too.
In Love Hurts, Skipper reveals that Kowalski has a tattoo of Doris the Dolphin (we never find out where).
In the commentary of the movies and in A Christmas Caper, he states his name, rank and serial number as: First Lt Kowalski, Serial Number 8-6-0-niner-bravo-alpha-mega-niner (860-NBA-MN).
Kowalski is dentophobic (irrationally fears dentists) - at the end of Needle Point, it is revealed that he has a phobia of dentists, which is peculiar in that, as Private soon states after Kowalski runs off, penguins don't have teeth. All animals in zoos need oral checkups, though, so Kowalski's fear is still somewhat rational.
He tends to say "Oh, Golly", "Good Golly" & "Mama", perhaps as a nod to Johnny Bravo. They are both voiced by Jeff Bennett.
The first time Kowalski made a mistake and was slapped by Skipper is in The Hidden.
He is shown to be jealous that the bad guys (like Dr. Blowhole) get the "good stuff".
In Operation: Cooties, Kowalski had to put a quarter in the show-off jar (because it must be implied that Skipper is annoyed that Kowalski keeps showing off his smarts to the other penguins).
In Night and Dazed, he reveals that he's able to read lips (not very well, though).
Kowalski usually explains things in a very complicated way (sometimes on purpose).
He's so scientific, his exclamations are related to science ("Newton's knickers!" "Einstein's undies!", It's About Time) and "Galileo Galilei!!" (Needle Point).
He seems to have learned how to read in later episodes, along with Private.
April Fools shows that he reads for a pastime (although it has been stated he can't read).
Perhaps he's learned to read sooner then that, but only in exotic languages such as French, for in the movie Madagascar 3: Europe's Most Wanted he was able to read the profile of Chantel DuBois perfectly while escaping Animal Control in Monte Carlo. This is a major contrast to in the original Madagascar movie, when he looks at a combination of English and bar codes as an "older code" that he has difficulty translating.
However, he had an alter-ego of himself called "Commander Kowalski" that seems more confident and notably better than his previous leadership ideas. (P.E.L.T.) It is unknown whether this is a recessive sub-personality or trying to prove to Skipper that he is trustworthy.
In Maurice at Peace, Kowalski starts sneezing as soon as he enters the florist's shop, suggesting he may have hay fever or some allergic reaction to plants or just general allergies caused by the pollen & dust.
Kowalski is a deep sleeper; even Julien's antics couldn't wake him up, as seen in The Helmet and Operation: Break-Speare as in the latter he doesn't seem to be suffering the detrimental effects of the severe degree of insomnia Skipper experienced.
In Loathe at First Sight, it is said that Doris gave Kowalski the "let's just be friends" talk 16 and a half times but he couldn't hear the rest because he was sobbing.
Upon being loyal to Skipper as a recruit, Kowalski has disobeyed him twice, one in Invention Intervention, where he built something after Skipper told him not to invent anymore, the other in The Trouble With Jiggles where he is found out for not destroying Jiggles.
He can be a little violent sometimes. Like in The Trouble With Jiggles, where he thought the children were eating the jiggli (they were really eating jello cubes) and was about to shoot them with a bazooka. He tried the same after Skipper blew up his hard drive in Good Night and Good Chuck.
Kowalski's way to relax is "pushing the untested boundaries of science", as per Action Reaction.
Kowalski fears head injuries due to harm coming to his precious intellect when not in headgear. Noted in Byte Sized where he cries "NOT IN THE BRAIN!" while trying escape a fish slapping from Skipper and, in Rock-a-bye Birdie, where he is hit by a bowling pin and responds "I'm ok, it's a non-brain injury."
He carries around a wombat brain & in Misfortune Cookie when he says that he doesn't know how swapping Rico's brain with it would help, Kowalski says: "Oh, I've got to do something with this" and holds up a jar with the brain in it.
Kowalski dismisses everything that goes against science, even when there's strong evidence he's wrong, he still refuses to believe it. Several occasions include Wishful Thinking, where he rudely rebukes Private's belief in magic, in Driven to the Brink, where he refuses to believe the car is haunted, even when he has no other explanations, and in Mental Hen, where he refuses to believe in Psychic Powers, even when evidence strongly pointed to its existence. Strangely, on two of these occasions, he proved to be right, as they were either accidents (Driven to the Brink), and the result flawless study (Mental Hen).
Kowalski desperately wants to be a leader and it is suggested that he thinks that Skipper is a 'dunder-brained boob'. (see P.E.L.T., Whispers and Coups, Snakehead!)
Kowalski has a widow's peak, which is where his black feathers form a V shape on his forehead. This widow's peak is very emotive, especially when he's serious or enraged.
It is revealed that he doesn't like broccoli in The Penguin Who Loved Me but he mentioned going "all in on the broccoli for lunch" in Operation: Cooties. It's possible that after Operation: Cooties he started to dislike broccoli.
"Kowalski" is a Slovian (n.e. Polish) surname, especially common among Jewish immigrants, subtly implying that Kowalski may be Jewish.
In conjunction with this, Jan Kowalski or Jan Nowak is the Polish equivalent to John Smith or Doe in English-speaking countries. (Kowalski means Son of Kowal, which in turn means Smith.)
However, he and the others always technically mispronounce his name, since in Polish, the letter "W" is pronounced like the English "V", and the stress is placed differently.
Kowalski is also a slang nickname for somebody who works diligently in the background and never takes any credit - which was applicable in the first movie, at least.
Kowalski always records his ideas or possible options on a clipboard notepad and a whiteboard. Most of what he notes down are usually drawings.
He holds it like a Russian abacus despite it looking like a Chinese abacus. (e.g. Kanga Management etc.)
He is ambidextrous.
He is able to make gadgets quickly using simple tools (e.g. Roomies).
Kowalski considers math to be a universal language as in shown in Roger Dodger.
The only leisure activity he would do with friends is trivia games, as stated in Kanga Management multiple times.
Kowalski is the tallest and skinniest penguin of the four.
He happens to give complex and complicated options sometimes which is a counterpart to Private's simple options (e.g. Maurice at Peace, Out of the Groove, etc.).
In Love Hurts he is one of the two penguins (him and Rico) that are in denial of going crazy for a girl.
Kowalski seems to have been trained in fencing, in the episode "The Hidden" he takes a fencing stance and says "en garde."
In Cute-Astrophe, Kowalski demonstrates he still has a high opinion of his own coolness level, attempting to dance to encourage the throwing of fish, even ready to slap his buttocks. Rico recoils from the sight, somewhat nauseated.
He analyzes simple things to a scientific level, such as that there is no museum in the zoo (Otter Gone Wild), who threw the mango seed (even though Julien actually didn't) (Gut Instinct), and declaring that gazillion doesn't exist (though it's just a figure of speech) (The Big S.T.A.N.K.).
Kowalski is the one who has kissed most throughout the episodes. The first episode was "Mental Hen", where the Blue Hen kissed him for being such a hot dancer. The second episode was "The Penguin Who Loved Me" where Doris kissed him, after she saw him fighting, causing them to date each other. This is also the episode where Kowalski has finally made Doris his girlfriend.
Kowalski is the least capable in Hand-to-hand combat (the second being Private/Rico), choosing to fight with weapons, machines & even his abacus.
It is shown in Lunacorn Apacalypse that Kowalski is taking/has taken an online class.
While all four of the penguins are very close to each other, Kowalski seems (somewhat) closer to Private than he does to Skipper or Rico.
