It's a Mad, Mad, Mad Galaxy: a collection of stories (1968.) Contents:

The Body Builders
The Planet Wreckers
The Star-Sent Knaves
The War with the Yukks
Goobereality

Stories are from 1963-1968: originally in Galaxy and Worlds of Tomorrow; "Goobereality" is original to this volume. This is the 1st time any of these appeared in a Laumer collection. ["The Big Show" is mentioned on credits page and back cover, but is NOT in this collection - it appeared in the 1972 collection The Big Show.] Most of these are Laumer in humorous mode.

(2 story summaries from back cover):
"The Planet Wreckers" - Jack Waverly goes to bed an ordinary mortal and wakes up a movie star. But the trouble is, his life is the price.
"The Body Builders" - Tired of being a 97-pound weakling? Just buy yourself the Body Beautiful.