Space Pirate Mito

Uchū Kaizoku Mito no Daibōken, released in English speaking countries as Space Pirate Mito, is an extremely obscure 1999 anime that lasted two seasons (split between the Winter and Summer TV seasons), each spanning 13 episodes. The series centers around Aoi, a fairly typical Japanese teenager whose father had passed on and whose mother, Mito, works overseas as a model. Only... his mom isn't really who he thinks she is.

In reality, Mito is known as the galaxy's most dangerous pirate with enough guts to outshine a supernova. She's a three foot tall childlike alien- yet all she really wants is to be called "Mom". When the Galactic Patrol follows her to Earth, Aoi is pulled into an intergalactic goose chase that brings him to all corners of the universe, along with the first working mom to carry a pulse rifle.

The series is a bit... odd, but still manages to be enjoyable with its colorful art style and strange cast of characters. Just don't try to make too much sense of the plotline. You will severely hurt your brain.

The series was released in English by Media Blasters, though with a 5-year gap between the releases of the two seasons. While an English dub was produced for the first season, Media-Blasters opted to release the second season sub-only, due to the changes in the anime market over that time period.

Tropes used in Space Pirate Mito include:

Absurdly Youthful Mother: Mito.
Adjective Noun Fred
Alpha Bitch: Kafuko, multiclassing into Rich Bitch. She becomes more of a Lovable Alpha Bitch as the series continues.
Battle Amongst the Flames: Aoi has flashbacks of his mother fighting Ranban amidst swirling flames.
Bizarre Alien Biology: The aliens that aren't Starfish Aliens or Intelligent Gerbils tend to have this. For instance, Mito's species determines its gender during puberty.
Cute Bruiser: Mito.
Dating Catwoman: Mutsuki Nenga, who falls in love with Aoi while going undercover to investigate the son of the infamous Space Pirate Mito.
Disappeared Dad: Aoi'd father died before the start of the series.
Dual Age Modes: Effectively Mito, with her Mail Suits.
First Law of Gender Bending: Poor Aoi. After he has to consciously choose to be male (long story about Bizarre Alien Biology) at the end of the first series, he finds out that it takes a while to settle, and he's Mode Locked as a very pretty girl. The second series is put in motion by Aoi's quest to become a man again.
Flashback Echo: Aoi has cryptic flashbacks through the first half of the series, to the battle between Mito and Ranban when he was taken into space as a child.
Giant Waist Ribbon: Mito wears a bow so large that its tails have little bows on them.
Go Mad from the Revelation: Ineffectual Sympathetic Villain Masatsuki Nenga goes totally batshit insane when he comes to the realisation that his "Justice" is nothing more than a tool of oppression (one that has no issue shooting down a "mob" of villagers, men, women and children) used by a pretender to the throne. This leads to about two episodes worth of him screaming "I AM JUSTICE!" at the top of his lungs while firing his gun like the lunatic he is. This would be fine all in all, but the guy doesn't look older than 12.
Gratuitous English: The theme song quasi-translates the series title as "Stellar Buster Mito". Several fansubs of the series followed suit.
I Am Spartacus: Combined with Lost in a Crowd during the second half of the first series. When the Galactic Patrol invades Aoi's hometown and demands that he surrender, his classmates from school put on Aoi masks and run out of the building. They get captured, but give Aoi time to escape.
I Take Offense to That Last One: A variation. When the Galactic Patrol is looking for Aoi, they announce his "crimes" to the general populace, hoping to flush him out. In order, this includes being the son of a wanted Space Pirate, seducing women, being a ten-foot monster (and apparently a gremlin), and disrespecting his parents, since he injured his mother and ran away. Hearing the announcement, his classmates ask if it's true, and Aoi replies, "It's true," but stops short, leading his friends to have Imagine Spots based on the more outlandish claims. (He really meant the last one, though the first -- and arguably the second -- are also true).
Mobile Suit Human: Mito uses a "Mail Suit" as Powered Armor - or just to pass as a normal, adult humanoid woman. The fact that she'd been wearing it around Aoi until the series started causes problems in their relationship. Especially considering that all the Mail Suits look the same.
Nice Job Fixing It, Villain: Aoi wears a bracelet that he believes is a good luck charm and the audience is led to believe is the key to a powerful weapon. He also starts having random bursts of powerful energy when the bad guys attack. Near the end of the series, Ranban removes this bracelet and tells Aoi it was an enhancer that brought out his powers, making him helpless without it. Cue Aoi causing an explosion with power even greater than he used before, and Mito telling Ranban that the enhancer was actually a limiter to keep Aoi's powers in check.
Override Command: The Mail Suits have a glitch triggered by hitting a sensor on the back; the glitch short-circuits the suit and paralyzes the wearer.
Pirate Girl: The titular character, along with several other members of her crew.
Puppet Gun: Not quite the same, but one spaceship can be used like a lightsaber by handling a model-sized version of the ship.
Really 700 Years Old: Mito is over ten thousand years old, but looks like she's in third grade. (And she's forced to start attending after a police officer spots her real form outside.)
The Resenter: Ranban's villainous motivation comes from being imprisoned because his body never settled on a gender, which drove him insane enough to get revenge by blowing up everyone else in the royal family of his planet. Only Mito escaped, and Ranban continued to pursue her, mostly because he resented the fact that she could rule the galaxy, while he was denied this right, despite the fact they were practically twins, except for the gender thing.
Samus Is a Girl: Played with. Big Bad Ranban's helmet is knocked off during a fight to reveal the face of Mito's Mail Suit; this is when the audience learns that all the suits are made with the same face. Ranban himself is technically a hermaphrodite, since his/her Bizarre Alien Biology never triggered the change at puberty that normally determines gender in his/her species.
Second Episode Morning: Played with. Mito, caught climbing out of her Mom suit by Aoi, at the very end of the first episode, tries to climb back in at the beginning of the second episode and assure her son that what he saw was just a dream. The two of them laugh it off until she realizes that her non-human crewmates are still hanging around. With no other choice, she shows him her true self (an alien that looks like a 3rd grader), causing Aoi to faint. The very next scene shows Aoi waking up screaming and deciding that he must have dreamt the previous scene. Until his house is destroyed by a giant version of his mom that suddenly takes to the air. Aoi flees, then is hit by a car, and then wakes up screaming again, this time for real. He hears his mom's voice from the other room, but when he sees her in her true form again, he leaps back into bed, hoping that this, too, is All Just a Dream. (It's not.)
Space Pirate: Mito and her crew.
Space Police: The Galactic Patrol.
Wingding Eyes: All the humanoid aliens in the series have starburst-shaped pupils. Aoi, who's half-human, has one normal pupil and one starburst.
Woolseyism: In the dub, Masatsuki calls his Robot of the Week creation-device "Mister Roboto", and even shouts "Domo-Arigato, Mister Roboto!" when using it. This reference was not present in the original Japanese.