One of the scariest things about “Treehouse of Horror XVII,” the annual “Simpsons” spookfest presented Sunday night at 8, is what those Roman numerals signify.

Yes, it’s true.

The Fox prime-time animated series, spun off from Matt Groening interstitials created for “The Tracey Ullman Show,” has been around since 1989.

This weekend, it presents its 17th consecutive Halloweenish special, where all bets are off, and in which the writers and animators get to indulge their wildest flights of fancy.

“The Simpsons” is the oldest scripted series running in prime time (NBC’s “Law & Order,” the next oldest, premiered a year later). Amazingly, all the principal voice talents – Dan Castellaneta, Julie Kavner, Nancy Cartwright, Yeardley Smith, Hank Azaria and Harry Shearer – are still with the show. For that matter, Bart’s still in grade school.

Today’s college students never knew a world without “The Simpsons” in it, and that familiarity with the residents of Springfield makes each show a treat, and these no-holds-barred “Treehouse of Horror” specials especially so.

Sunday’s edition opens like HBO’s “Tales From the Crypt,” but with decrepit Mr. Burns as the Crypt Keeper. Moe the bartender is his torture victim, whose spilled blood spells out the special’s “Treehouse of Horror XVII” title.

“Look at that!” Moe says. “My blood’s a genius. Roman numerals and everything!”

As usual in these annual anthologies, three stories follow.

The most controversial is the final one, “The Day the Earth Looked Stupid,” set in Springfield in 1938. It’s the night Orson Welles broadcast his infamous “War of the Worlds” radio scare, and this time real aliens – you’ll recognize them from their green tentacles and salivating mouths – use the hoax as cover to launch a real invasion.

Three years later, with Springfield still decimated, one alien complains to the other that the plan doesn’t seem to be working.

“The earthlings continue to resent our presence,” it says. “You said we’d be greeted as liberators.”

“Don’t worry,” the other replies, holding up human organs as visual aids. “We still have the people’s hearts and minds.”

The other stories are “You Gotta Know When to Golem,” which makes great use of guest voice Fran Drescher, and “Married to the Blob,” which does the same with Phil McGraw and Sir Mix-a-Lot.

Watch, and you’re guaranteed to Laugh-a-Lot.

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THE SIMPSONS

8 p.m. EST Sunday

Fox