The Characters

Stanley H Tweedle
Ex-security guard class 4, ex-Austral B heretic and current captain of the Lexx. The only member of the crew to be entirely human, Stan was forced to become a security guard when caught by His Shadow's forces whilst smuggling the amino acid codes for the Lexx to the heretics. Luckily for him, he wasn't executed for this heresy just in case His Shadow ever needed any more information from him. Although this sounds brave, Stanley H was really only in it for the glory and indeed the free sex on accommodating pleasure cruisers. He only got involved with the Lexx theft due to poor timing - he was due to report for punishment (triple organ donation) when the whole thing erupted around him and he was swept away. Due to an accident he is also now the only member of the crew who can command the Lexx.
Stan is self-centered, vain, old, unattractive (Xev's words, not mine) and his propensity for self-preservation is quite extraordinary, but as we see more of Stan, we realise his heart is in the right place, and he's trying to become a bit more heroic, he really is...
Xev Bellringer
Xev Bellringer was brought up in a box at a holocare home for trainee wives, due to her "not working out" the way her parents expected. Unfortunately her pre-pubescent husband dumped her at the altar (to be fair she was slightly unattractive, to put it mildly) and she therefore punched him out. This resulted in her being sentenced to become a Love Slave, but again, thanks to the antics on the Cluster during her transformation, she got the looks and the sex drive, but managed to miss out on the personality "adjustment". As an added bonus, she also got some Cluster Lizard DNA which means you don't really want to be messing with her.
Xev is in her third incarnation already. She was originally known as Zev, who was the girl who got transformed into the beautiful love slave. Unfortunately, Zev was killed saving Kai's "life" when a team of mad doctors trying to get their hands on the Lexx were about to pulverise his atoms. Luckily, a carnivorous plant with the ability to reconstitute proteins (handy) rebuilt Zev from the goo that remained, and she became the Xev that we all know today.
Xev cares deeply for her fellow crewmates, even Stan who has by now almost stopped attempting to get her into bed. She is also passionately in love with Kai, who, unfortunately, is dead...
Kai, Last of the Brunnen-G
Last of a race of romantic dreamers, Kai was killed by His Shadow 2,000 years ago during a futile attempt to defend his planet against His Shadow's forces. The planet was destroyed and Kai's body was taken and turned into a mindless assassin. When the heretics took over the Lexx, Kai was chosen to hunt them down, but unfortunately for His Shadow, Kai regained the memory of his former life and realised that His Shadow was a Bad Thing. He joined the crew of the Lexx by default really, having nothing better to do at the time.
Kai has completely come to terms with the fact that he's dead, and therefore has no personal agenda. He sees to it that the crew come to no harm, and has a very well developed sense of duty and justice. Of course this doesn't always work to the crew's advantage, especially if they're trying to get away with something that Kai doesn't think they should be allowed to get away with. Being dead, his body is in constant danger of degenerating, and to this end he sleeps in a cryopod when not needed, to preserve his supply of "Protoblood", the substance which keeps him "alive". Kai has no motivation, no real emotions, and can be frustratingly obtuse sometimes, all of which conspire against Xev when she's trying to get him into bed. He does however have an endearing habit of going completely mad at the most inopportune moments.
790 is the robot, or robot head anyway, that suffered the personality adjustment that Xev was supposed to get, after his body unfortunately got eaten by a Cluster Lizard. The personality adjustment meant that he fell totally in love with Xev at first sight, and was besotted by her. He hates Stanley, who is the nearest thing to a rival that he has, but tolerates Kai as he shows no interest in Xev and has in fact saved her life on a number of occasions. He has an unending store of terrible poetry, all of it about Xev, and makes Stan's life a misery at every possible moment. His greatest desire is to find a headless body and attach himself to it so that he can make sweet sweet lurve to Xev. In series 3 he suffers a nasty accident which leaves him rather broken after falling off the edge of the bridge, meaning that Kai has to fix him.  Unfortunately for Kai, as the little robot head re-boots it's love slave programming also re-boots and now 790 is fixated on Kai. And thinks himself female. Poor poor 'bot.
Lexx is a bio-mechanical spaceship and the most powerful weapon known to man. It was grown on the Cluster by His Shadow who intended to use it to blow up any troublesome planets that got a bit lippy. He is not the brightest of spaceships, and has a habit of accidentally blowing things up (usually planets) if not instructed very clearly by Stan, who is now his master. Being bio-mechanical, Lexx's fuel is organic material and he needs to eat regularly to build up reserves. This involves him sometimes detouring a little to pick up tasty "snacks" such as garbage planets, other spaceships, genetic waste pods, and theatres. In season 3 the Lexx is out of fuel to such an extent that he cannot move anymore and is stuck in orbit until the crew can find something for him to eat.
His Shadow/Mantrid
His Divine Shadow was the nasty evil ruler of the League of 20,000 Planets. He was a being who could transfer his essence from one body to another, making him effectively immortal. The reason for this was that His Shadow was actually an insect; a lone survivor of the insect wars which the Brunnen-G had won thousands of years ago. The insect passed its essence into a human host and created the Divine Order which was eventually destroyed by Kai. His body dead, His Shadow passed his essence back into the insect body that he's originally come from that had lain dormant but growing for thousands of years under the Cluster. This was the Gigashadow, a very large and angry insect that intended to wipe out the whole human race, and was doing quite a good job of it until it was destroyed in a collision with the fractal core whilst trying to catch the Lexx. Part of the insect essence was passed to Kai, unbeknownst to him, forcing him to go back to the cluster to try to find another insect to pass it on to. The larval insect that Kai discovered was taken to Mantrid, a bio-vizier who had been imprisoned years ago by His Shadow for being too dangerous. When the insect larva was reanimated, and Kai mortally wounded Mantrid, Mantrid's assistant used the insect's transferrence organ to transfer the mind of his beloved master into a small pod-like machine that Mantrid had been going to use as an escape vessel from the prison. This left Mantrid a confused chap, now being part man, part insect, part machine and all bad, inheriting the insect's hatred for all humanity and being intent on its complete and utter destruction.
Lyekka is a flesh-eating plant who reads dreams to find prey. When we say flesh-eating, we actually mean man-eating, but she would eat animals if there was nothing else. She arrived on the Lexx in a pod which was attracted there by Stanley's dream of Lyekka, a girl he went to school with. The plant took on the form of Lyekka and this is her chosen form to appear in, although her natural state seems to be almost liquid and she can take on other forms. Stan is very keen on Lyekka, even though she has no sexual organs, and Lyekka seems to also like Stan, and doesn't want to eat him unless absolutely necessary. Lyekka has the ability to recreate proteins and it was her who brought Xev back to life when she had been pulverised into protein goo, as a gift for Stanley. She also would not eat Kai, because he is dead. She has been very useful on a number of occasions by eating unwanted guests on the Lexx. When not hungry, she stays dormant in her pod, which hangs high above the bridge of the Lexx, emerging every now and again to eat.  At the end of season 2 Lyekka shows bravery beyond the call of duty by sabotaging Mantrid's attempts to destroy the Light Universe and gives her own life. But of course on the Lexx people don't always stay as dead as they were.
In Season 3, Prince is the "Ruler" of the Fire planet and the one who first manages to get aboard the Lexx and bring the crew back to Fire. An odd character is our Prince, very seductive and empathetic (especially with Xev) but at the same time cold, hard, cruel and "good with pain". He controls the precious supply of water on Fire and is constantly in danger of losing his power due to takeover bids staged by other rulers on the planet. His only goal seems to be to destroy Water. Whether this is jealousy of its plentiful lifestyle or whether there is another reason becomes clearer towards the end of the season. When angered he has a lizard-like ruff which extends from the back of his neck, but he doesn't tend to stay angry for long as he'd rather do something about it. Like kill someone.
Prince is also, it turns out, unkillable. Well, he's easy enough to kill it's just that he doesn't stay dead. He can reincarnate wherever and as whoever he pleases, which you can imagine causes all sorts of trouble for our beloved Lexx crew.