De Lorean, gorillas, Grant and Lee, and more; While Reagan Slept, by Art Buchwald. New York: G. P. Putnam's Sons. 334pp. $14. 95.

What do Senator Beenbag and Mr. Digging of the EPA Mudslide Division have in common? They're both fugitives from Art Buchwald-the-rogue's gallery - running through the cheeky cherub's collection of published columns, ''While Reagan Slept.''

Where but in Buchwald could you find six men in asbestos Brooks Brothers suits, dousing political fires in the White House? Or hear the disenchanted voter lamenting, ''He promised us a rose garden, and all we got was cheddar cheese?''

But nobody could be mad at Mrs. Buchwald's little boy Artie for long. If the political ribbing rubs, chuckle at artist Steve Mendelson's sketches, reminiscent of 18th-century Isaac Cruikshank's eat-drink-and-be-merry caricatures.

Come to think of it, the cover photo of Buchwald in striped nightshirt is almost worth the price of the book.