The character of Harry Solomon is played by French Stewart.
Harry is the fourth and, by general consensus among the aliens, least important member of the expedition. Initially it is suggested that he was brought along because 'they had an extra seat.' We later discover that he does indeed serve a role that is important to the mission. He carries a giant transmitter, implanted in his head (in the part he doesn't use - the brain) which enables the aliens to communicate with the home planet.
On Earth, Harry assumes the role of brother to Dick and Sally, uncle to Tommy. In the early episodes Harry notes his lack of any definable role in the mission and the other aliens struggle to rectify this - sending him to art classes which he proves to have quite a talent for. On one occasion Dick demotes him to the role of son; on another occasion he promotes him - to the role of Harold!
An example of Harry's initiative is seen early on in the series. When the aliens arrive and settle themselves in at Mrs Dubcek's apartment, he volunteers to draw up an itemised inventory of which common household products are toxic and which are not. He does this by consuming each and every one.
There's no arguing that Harry is an idiot but he provides the most fun in terms of sheer comic entertainment. On occasion he exhibits frighteningly profound insight. He has a warm personal touch and Earth women are bizarrely drawn to him. Just ask Cindy Crawford.
In terms of romantic and/or sexual encounters of the alien/human kind Harry easily has the upper hand on the other member of the mission. He is the first among them to experience that human sensation of 'getting laid.' He has dalliances with countless women - and possibly one or two men. He has a brief but memorable fling with Nina, which ends abruptly after a tragic misunderstanding involving a certain 'tooth fairy'.
All in all, Harry's character seem to confirm a certain perception that women are drawn to men who don't think too much; that intellectualism is off-putting where women are concerned.
The real love of his life during his time on Earth is undeniably Vicki Dubcek - the landlady's daughter. Unfortunately he has to give her up when fate and the Big Giant Head intercede.
Harry Solomon is one-of-a-kind as TV sitcoms go. A truly brilliant comic creation played to perfection.