When it comes to Harvard-Yale, even the tailgates are institutions.

This Saturday will mark the 40th time that Richard Sperry ’68 and Roger Cheever, Harvard ’67, tailgate The Game. The two friends have been tailgating the storied rivalry since 1972 and haven’t missed a game since.

Wait, 1972? Wouldn’t that make 2013 their 41st consecutive tailgate? Sounds like some Harvard math to us.

This isn’t a mistake, though. The pair celebrated their 40th consecutive tailgate in Cambridge last year. But Sperry, the Yalie, wasn’t going to let that dampen this year’s festivities at his alma mater.

“Never mind the fact that we celebrated our 40th in Cambridge last year,” reads the email invitation to the tailgate. “We had a great time, and we’re simply just going to do it again this year in New Haven.”

That’s the kind of spirit that pervades Sperry and Cheever’s annual party, which they now host with accomplice John Steffensen ’68. Despite their opposing allegiances, the two make sure that the tailgate is about fun and friendship. For these two, rivalry is just an excuse to get together in the first place.

Ultimately, says Sperry, “It’s just about renewing friendships.”

Sperry met Cheever while the two were training as officers in the Navy. They became fast friends and attended that first Harvard-Yale game while living together in Boston in 1972 — Yale won, meaning Cheever had to pay for the tickets. But the next year, in an effort to recoup his losses, Cheever insisted that they attend The Game and make the same bet again. The rest is history.

“The very beginning tailgates are a bit of a blur; it’s so many years ago. I think it involved alcohol and not a lot of food,” Cheever now recalls with a laugh.

The tradition actually traces its origins to before the two even met. Sperry would attend Yale’s home games with his roommate and his roommate’s parents. The group would set up in Lot B, next to Cox Cage. Sperry and Cheever have claimed the spot as their own for the 20 Yale games they have since attended. Since the tradition’s inception, friends and wives have been added to the mix, along with a host of others. It is now a tailgate of truly epic proportions.

“Last year, at Harvard, at best guess we had over 150 people there,” Cheever says. It’s not just how many people show up: Who those people are can be equally impressive. Sperry and Cheever can now claim as guests Rick Levin, Tommy Lee Jones and the Bush twins, who brought along a few guests of their own.

“We wound up with six Secret Service agents with wires behind their ears, trying to look inconspicuous,” Sperry explains with a chuckle. “But they weren’t inconspicuous.”

The blend of both Harvard and Yale fans is notable as well. Few tailgates attract such a diverse crowd, but the convivial attitude that Cheever and Sperry work hard to maintain draws in fans of all stripes (Sperry says even their Princeton friends have started attending).

Key to maintaining this friendly mix is Cheever’s “Commencement Punch,” a family recipe handed down since Prohibition that Cheever makes for The Game every year. It’s a blend of rum, honey and fruit juice, and — according to Cheever — has received nothing but rave reviews.

“No one has ever refused a glass,” he attests with pride. And while the tailgate in its early years included the standard assortment of finger foods and beer, its menu has since expanded to include steak sandwiches and wine. (The hosts refer to the latter as “our acclaimed ‘Boola’ label.”)

Only once has the tailgate tradition nearly been broken. A few years back, Cheever’s son was playing in the New England Football Championships on the same day as The Game, which was at Yale.

“There lies a moral dilemma,” Cheever now remembers. “Does one support one’s family, or does one stick with tradition? And we basically did both.” The two managed to finagle their way onto the field at the Yale Bowl at 8 o’clock that morning, where they had a drink and tossed around a football before Sperry drove Cheever directly to Union Station where he caught a train north in time to make kickoff at his son’s game.

“We now say that we’ve gotten together on game day for 42 years for this ritual, which is absolutely true,” Cheever says. And they don’t plan on stopping. At one point, Sperry recalls, they had a conversation about how long the tailgate would continue, eventually deciding they could see themselves continuing for 50 years. But as that milestone approaches, neither sees any reason to stop.

“I think we’ll keep on doing it for as long as we can, because it’s fun,” Sperry says.

But the inevitable question remains: Where is the venerable tailgate most fun?

Cheever is hesitant to answer. “I have to really think about it,” he murmurs, before eventually settling on his alma mater.

For Sperry, on the other hand, the answer is an easy one. “I would say it’s more fun at Yale,” he says, his smile palpable even over the phone.