“The World’s End” opens Friday at Point, Eastgate and Star Cinema. R, 1:49, three stars out of four.

Edgar Wright’s three films with Simon Pegg and Nick Frost has been called his “Cornetto Trilogy,” named after a popular brand of ice cream in Britain. It’s an apt title for films that are meant to be pure, sugary entertainment, whether a zombie movie parody (“Shaun of the Dead”) or action movie pastiche (“Hot Fuzz”).

But there’s a bittersweet ripple in “The World’s End,” the third and supposedly final of the films, that gives it an extra poignancy. First off, Wright holds off the fantastical elements of the movie as long as he possibly can, instead focusing on the flailing attempts of five middle-aged friends to reconnect with their younger, happier selves.

In particular, Gary King (Pegg) is a train wreck — he was the coolest guy in high school back in the boys’ hometown of Newton Haven, sporting sunglasses, a black trenchcoat and a Sisters of Mercy T-shirt.  Twenty years later, he’s a middle-aged man, still wearing those sunglasses, trench coat and T-shirt. Not as cool.

Life has passed Gary by — his friends (Nick Frost, Paddy Considine, Eddie Marsan and Frost) all have careers, families, lives. Gary has hazy memories of better days. They look at Gary with a disdainful pity, which is why, when Gary cajoles them into returning to Newton Haven for an epic 12-pub pub crawl nicknamed the Golden Mile, they reluctantly agree.

This all isn’t just prologue — it’s nearly the first half of the movie, and it’s tremendous fun to watch five top British actors ping-ponging witty lines off each other, as the pathetic depths of Gary’s life is revealed to the other four. He wants to go back to those heady teenage days, but Newton Haven has changed since they all left — nobody remembers them, and the town feels cleaner, nicer, “Starbucked.” If you’ve ever gone back to your hometown, and tried to reconcile that street map in your head with the one in front of you, you’ll know the feeling.

“World’s End” makes a canny move in flipping the usual Pegg-Frost dynamic — this time Frost is the level-headed straight man, and Pegg the manic screw-up. Add in Considine, Marsan and Freeman as middle-aged men who slowly reveal their own regrets, and Rosamund Pike as the girl at least two of them were pining for, and you already have enough for a good movie.

And then the fantastical elements kick in, which I won’t reveal even though the trailer pretty clearly does. Suffice to say that what was a mordant comedy about getting old turns into an action romp, complete with frenetic fight scenes, explosions and lots of blue goo flying about. The hilarious thing is that in the midst of all the mayhem, Gary doggedly insists on seeing the pub crawl through to the end, so as the threat grows larger and larger, the lads get drunker and drunker. Maybe not the worst plan.

LIkewise, Wright and Pegg’s screenplay never loses that emotional thread they started with. If “Shaun” was about the aimlessness of misspent youth, and “Fuzz” was about rebelling against the stuffiness of small-town life, “End” is about the fragility of friendship over time, and the dangers of living entirely in the past. Between these films and “Scott Pilgrim Versus the World,” Wright has become very deft at using genre conventions to illustrate the human comedy while still giving his audience a ripping good time.

“World’s End” is decidedly less bloody and more sentimental than its predecessors, suggesting a certain mellowing with age. It’s not perfect — its denouement tries to hastily cram about an hour’s worth of exposition into the last five minutes — but it never loses its cheeky charm. If this the last of the “Cornetto trilogy”, time to hoist a pint to a fun, fruitful collaboration. Cheers.