Keith Laumer: The Lighter Side (Vintage Paperback) by Eric Flint

Two complete novels in one volume feature hapless heroes caught in an out-of-kilter spacetime clockwork: Chester W. Chester IV, who has inherited his great-grandfather's lifework--a super computer that can bring any situation or time to life; and Roger Tyson, who is being pursued through time by a motorcycle-riding, rutabaga-like alien in a world where eras millions of years apart have been combined into an insane smorgasbord of eons.

Contains:
In the Queue
The Planet Wreckers
The Body Builders
The Devil You Don't
The Exterminator (aka "A Bad Day for Vermin")
The Big Show
Goobereality
Prototaph
The Great Time Machine Hoax