Quoted from the Official Space Quest FAQ
I once wrote (and is still available at many SQ fan sites):
The Two Guys from Andromeda, or Mark Crowe and Scott Murphy as they're often mistaken for, are the glorified creators of the Space Quest series. Scott Murphy was a veteran programmer at Sierra On-Line, and Mark Crowe was a graphics designer for Sierra. After the completion of Space Quest IV, Mark moved to Sierra's sister company, Dynamix, and did Space Quest V on his own. But between then, they had worked together on Space Quest games for five years.
Scott first met Mark when he was designing the graphics for "The Black Cauldron". Scott was debugging the program. He and Mark got together and decided to do a game of their own, in their favourite genre - science fiction. But when they approached Ken Williams with the proposal to do a humorous science fiction game, Ken told them no. A funny scifi game just wouldn't sell, he said. But The Two Guys were determined and went on to program the first four rooms of the Sarien Encounter in their spare time. Scott programmed, Mark did graphics and Ken loved the demo and gave them green light to proceed.
After work on Space Quest IV was finished, the Two Guys from Andromeda suddenly split up. Scott Murphy left Roger Wilco indefinately, and Mark Crowe moved to Sierra's sister company, Dynamix, in Oregon.
So, Mark Crowe put on a flight suit and flew Space Quest V solo as his first Dynamix-job. Although Space Quest V was labelled a Sierra product, it was produced by Crowe and his buddies over at Dynamix.
Once SQ5 was completed, the Space Quest series was handed over to the sweaty palms of Josh Mandel, who had been a contributing writer on most Sierra games produced around the early 90's, including Space Quest IV. The game that was to become Space Quest 6 was the initial brainchild of Josh, but Scott Murphy gradually moved his way up to becoming co-designer, and finally - when Josh Mandel left the project before its completion - Scott became the sole designer and project leader.
Space Quest 7 was supposed to be helmed by Scott Murphy and newcomer Leslie Balfour, who up until that point had been manual writer (and responsible for a few weird jokes in SQ6, including the infamous "in space, no one can hear you clean"). The project got off to a bad start when Sierra management - recently purchased by conglomerate CUC Software, and later sold off to French company Havas - demanded a multiplayer function be implemented, severely limiting the design potential of the game the two designers had in mind. Everything came to a screetching halt on Christmas eve 1997, when Scott Murphy was informed by the brass that the project had been cancelled.