Having developed skills using an airbrush, he began painting T-shirts at custom car shows, where he met and then worked with Ed Roth, the leading exponent of Weirdo Hot Rod art.
Settling initially in Oakland, Mouse met Alton Kelley, a self-taught artist who recently arrived from Virginia City, Nevada, where he joined a group of hippies who called themselves the Red Dog Saloon gang.
The psychedelic posters Mouse and Kelley produced were heavily influenced by Art Nouveau graphics, particularly the works of Alphonse Mucha and Edmund Joseph Sullivan.
Producing posters advertising for such musical groups as Big Brother and the Holding Company, Quicksilver Messenger Service, and Grateful Dead led to meeting the musicians and making contacts that were later to prove fruitful.
In 1971, Mouse returned to California, living near Kelley in Marin County, and the pair resumed their partnership, producing commercial artwork related to the Grateful Dead and later Journey.
The pair are credited with creating the skeleton and roses image that became the Grateful Dead's archetypal iconography, and Journey's wings and beetles that appeared on their album covers from 1977 to 1980.