Shot through a wormhole to the other side of the universe, Commander John Robert Crichton Jnr has somehow managed to keep his hide, his sanity and his sense of humour intact through three years of trials.

That�s apart from the times he had hallucinations, or died, of course. But he has always kept his sense of humour, along with his two burning obsessions - wormholes and Aeryn Sun.

At the start he was merely an incompetent abroad, but being a man of intelligence (he's got a Doctorate in Theoretical Sciences) he adapted quickly. By the end of season one Moya's crew found themselves following his plans more often than not, whatever reservations they may have had about their wisdom.

Crichton is especially prone to having his head messed about with. Twice he's thought that he's back on Earth; on one trip he was the guinea-pig of a race of Ancient Ones; another visit was a Scarran-caused hallucination. Then there's the wringer that Scorpius put him through...

Season two saw him getting a lot closer to Aeryn, but the path of true love wouldn't run smooth. It turned out that his escape from Scorpius hadn't been as total as he thought, as the pitiless scientist had implanted a neural clone in his head in order to retrieve Crichton's wormhole knowledge.

As the clone infiltrated Crichton's brain, he became more and more erratic, driven to distraction by visions of Scorpius. Finally it took him over, putting Aeryn in a position which led to her death. Only Zhaan's intervention brought his love back from beyond.

Largely freed of the clone, and in control of its weaker echo, dubbed Harvey by Crichton, his quest for the secrets of wormhole science took him and everyone else on Moya into danger, and finally led to Zhaan's death. Things got even stranger when Crichton was twinned into two identical versions of himself.

While one version ended up on Talyn, blissfully bonding with Aeryn, the other was left behind on Moya, bitterly cursing his double. Moya-Crichton was the lucky one though. A battle to stop the wormhole knowledge left locked in his brain from reaching the Scarrans left Talyn-Crichton dead in Aeryn's arms from radiation poisoning.

When Aeryn finally returned to Moya, Crichton hoped he and she could pick up where they left off. Her coldness to him, born out of seeing him as her dead lover, upset him deeply. That was nothing to the revelation that she was pregnant with his double's child, imparted to him too late to stop her leaving.

Crichton's work with wormholes continues to go well. Whether his attempts to get over Aeryn will be as successful remain to be seen.

Key episodes: Premiere, A Human Reaction, Nerve, The Hidden Memory, Look at the Princess trilogy, Won't Be Fooled Again, Die Me, Dichotomy, Self Inflicted Wounds parts 1 and 2, Green-eyed Monster, Infinite Possibilities parts 1 and 2, Revenging Angel, Into the Lion's Den parts 1 and 2, Dog With Two Bones, Crichton Kicks.

Find out about the man behind the astronaut in our actor profile of Ben Browder.