While playing for the Vancouver Whitecaps, he once mooned the Seattle Sounders bench following a goal, and on another occasion took a swig from a fan's beer before taking a corner kick in San Jose, setting up a goal from the set-piece. Johnston was a key member of the 1979 NASL champion Vancouver Whitecaps alongside the likes of English World Cup winner Alan Ball, helping them defeat the New York Cosmos in the semi-final, and then the Tampa Bay Rowdies 2–1 in Soccer Bowl '79.