There are chuckles coming out of the foxholes this week in the beleaguered Environmental Protection Agency, where the troops are passing around a tongue-in-cheek memorandum prompted by "the regrettable Ted Simmons incident."

"Ted Simmons," of course, is the EPA bureaucrat in the popular comic strip "Doonesbury," who demonstrated his distress over budget cuts by perching woefully on the window ledge outside his office, pondering the ultimate RIF.

Because of Simmons (whose boss couldn't even remember his name and called him "Simpson" in the comic strip denouement), "We have been forced to impose new security practices on window and window ledge use," says the memo, purportedly from the office of John P. Horton, an assistant EPA administrator.

Ledge-sitters, it says, "must be given the choice of jumping or being pushed." The memo makes an egalitarian attempt to accommodate "those individuals with creeds which require access to ledges," suggesting they might try the Crystal City facilities, which "are significantly higher, and their use will result in a greater likelihood for success for administration holdovers who are seeking new opportunities."

Horton's secretary hastened to disavow the memo yesterday. "It's not an official memo," she said. "It's undated. His memos are not undated." Besides, she said, "None of our windows open."

But Horton, a Reagan administration appointee, took the faked memo with the utmost magnanimity. "I just came in off the window ledge," he said. "What can I do for you?"