Christopher Guest’s mockumentaries (“Best in Show,” “A Mighty Wind,” and especially “Waiting for Guffman”) are among the funniest films of the last 15 years, and Fred Willard is generally the best thing about them. But unlike his co-stars, who seem to make a point of trying on different personalities in each film, Mr. Willard sticks with the gauche blowhard, the Ugly American who knows less and talks more than anyone else in the room.

In the fairly embarrassing “Elvis and Juliet,” a play written by his wife (Mary Willard) and receiving a leaden production by the Abingdon Theatre Company, that persona is trotted out once again. But not even the sight of Mr. Willard in a 1970s-era Elvis Presley jumpsuit can keep this vehicle from teetering perilously close to the realm of “Red, White, and Blaine,” the amateurish community theater production at the center of “Guffman.”

Actually, this vehicle is a two-seater, as Mr. Willard shares the stage with David Rasche as Art and Joey Lesley, two perma-tanned ring-a-ding-dingbat brothers who have a tribute act in Las Vegas. The pair croons and cavorts their way through a limp retelling of two oil and-water families who meet when Elvis (Haskell King) gets engaged to Juliet (Lori Gardner). Her parents are Connecticut academics who bicker in Latin; his are lounge lizards who tell dirty limericks and say things like “Put some gasoline in my tank.”

Actually, the Connecticut father responds to the above request by bringing out – ready for this? – tea instead of booze. Juliet’s little brother then does a hip-hop rendition of Poe’s “The Raven.” (Ms. Willard has somewhat inexplicably set “Elvis and Juliet” in 1989, even though it alludes to an Elvis postage stamp that was issued in 1993 and features the image of a greatest hits album released in 2002.)

Everything gets resolved in the space of about three underdeveloped minutes, but not before Mr. Willard flubs a half-dozen lines; with the exception of that racy limerick, he never comes close to the blissfully oblivious state familiar from his largely improvised film work or from his performance as yet another would-be in-law on CBS’s “Everyone Loves Raymond.” (Perhaps that side will resurface on June 19, when Mr. Willard “and friends” will perform a night of improv as a benefit for the Abingdon.)

Mr. Rasche’s hammy, Rat Pack-era suavity and an enjoyable slow burn by Warren Kelley as Owen, Juliet’s incredulous father, go only a tiny way toward redeeming Yvonne Coneybeare’s poky staging and at least one dreadful central performance. And the dialogue!

ELVIS: Juliet, my family is very odd. Idiosyncratic. Peculiar. …
JULIET: I love a man who knows his adjectives.

OWEN: You know what they are? They’re anti-semantic!
ART: Hey! I like Jews.

It’s during moments like these in “Elvis and Juliet” that a different bit of dialogue springs to mind. This quote comes from Mike LaFontaine, the boorish manager played by Mr. Willard in “A Mighty Wind”: Wha’ happened?

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