Dumb and Dumber To” partied like it was 1994 at the box office this weekend.

The sequel to the Clinton era smash injected life into Jim Carrey’s moribund career, reminding audiences why they once loved the silly putty faced comic genius. It was the weekend’s highest-grossing film, picking up $38.1 million despite stiff competition from “Big Hero 6” and “Interstellar.”

So how did the follow-up to a film that premiered 20 years ago before the dawn of DVDs, iPads and Facebook draw a crowd? Here’s four reasons why Harry and Lloyd stayed fresh:

1.) Accept No Substitutes

Unlike the doleful prequel “Dumb and Dumber: When Harry Met Lloyd,” the latest installment brought back stars Carrey and Jeff Daniels, as well as directors Peter and Bobby Farrelly. That kept the gross-out tone consistent and let viewers know this wasn’t a cheap ploy to cash in on nostalgia. That help explains why other long-gestating sequels such as “Blues Brothers 2000” or “Dirty Dancing: Havana Nights” failed to catch fire. It also might be a warning to studios looking to reboot past hits such as “Ghostbusters” without the original casts.

“Certain films are about more than just a concept,” said Paul Dergarabedian, senior media analyst at Rentrak. “They’re about the stars. For a comedy like this, you can’t just plug in any two guys into those roles.”

2.) Cable is King

The ubiquity of “Dumb and Dumber” on cable channels such as TNT and TBS, as well as its strength on VHS and other platforms helped the two dim-witted characters remain relevant.

Indeed, pay TV and home entertainment, even in its diminished, post-DVD crash form, has helped a number of titles in recent years build on their theatrical audiences. “Zoolander,” “The Shawshank Redemption” and “Anchorman” all developed broader followings thanks to re-runs and rentals after disappointing at the ticket booth, with “Anchorman” getting a sequel on the strength of that popularity.

“Generations grew up on ‘Dumb and Dumber,'” said Jeff Bock, an analyst with Exhibitor Relations. “It’s been playing on cable for the last 20 years and that wove these characters into the public consciousness and made them beloved.”

It also helped the movie attract younger audiences. Its opening weekend crowd skewed older, but the film still managed to draw ticket-buyers that weren’t even alive when the first film came out in 1994. Forty three percent of the audience was under the age of 25.

3.) Timing is Everything

It’s been two and half months since the last broad studio comedy hit theaters with “Let’s Be Cops.” In the meantime, the multiplexes have been dominated by dark thrillers, adult dramas and horror films. After all, it’s hard to crack a smile while watching “Gone Girl” or “Annabelle.”

That’s an eternity between comedies and it’s a gap that widened after Sony Pictures announced that it was pushing its Seth Rogen and James Franco assassination laugh-fest “The Interview” from October to December.

The lack of funny movies helped create pent-up demand for “Dumb and Dumber To.” It could also help “Horrible Bosses 2,” which debuts before the Thanksgiving holiday.

“It was perfect timing for a comedy,” said Nikki Rocco, distribution chief at Universal Pictures, the studio that is handling “Dumb and Dumber To’s” release. “The core audience wanted more and they got it.”

4.) Pinch the Pennies

Revisiting a beloved comedy 20 years after the fact could have been a disaster, but the film’s backers, Red Granite Pictures, wisely kept a tight lid on costs. The film carries a meager $40 million budget — a testament to new studio economics given that in his heyday, Carrey commanded $20 million a picture. Carrey’s inconsistency at the box office thanks to flops like “Mr. Popper’s Penguins” and “The Incredible Burt Wonderstone” made that kind of payday inconceivable.

But look at those grosses. In a single weekend, “Dumb and Dumber To” has earned $47 million globally, making it likely that it will turn a profit even with “The Hunger Games: Mockingjay — Part 1” set to crush everything in its path when it debuts next week. There’s nothing dumb about that.