Slagle was born in Detroit, Michigan, and adopted by a middle-class family, living in the blue collar area of South Suburban Detroit known as Downriver. He was raised in Trenton, Michigan, graduating from Trenton High School in 1976. He briefly attended the University of Michigan, and eventually dropped out without a degree in 1979 to become a fringe part of the Detroit Punk scene in the band Boris Savage and the Primates.
In 1979 he started performing at the open mic nights at Mark Ridleys Comedy Castle in north suburban Detroit. As stand-up comedy clubs exploded around the country during the comedy boom of the 1980s, there were plenty of venues looking for comics, and by 1983, Slagle was traveling the country as a professional comic. After three years of living on the road, he settled in Chicago, where he became a regular in the Zanies chain of comedy clubs.
In 1996, he appeared on-stage in a small theater in Chicago, with comedian Tom Naughton in the Slagle Naughton Report.
In 2000 he also produced and starred in a brief run on local Minneapolis television show: The Mudslingers Ball, with Lewis Black, Will Durst, Jeffrey Jena, and host Mike Lukas. It aired on KSTP channel 5, an ABC affiliate.
Slagle describes himself as right-wing, although the Libertarian Party claims him as their own. His politics seem right in line with the Libertarian platform, and although he occasionally appears at Republican political functions, he has never disowned his affiliation with the Libertarians.