Greek Wedding

Short Answer; Paris' wedding.

In the first movie, Toula gets married at a Big Fat Greek Wedding. In the sequel, hr parents get remarried at a Big Fat Greek Wedding.

Now, they are making a third. In the other two movies, we meet Toula's daughter Paris. By the end of the second, she has started to date and gone to college.

So what has to happen in the third movie is Paris' Big Fat Greek Wedding.

The movie has actually been announced, and the plot is said to be a family reunion in Greece after the death of Toula's father (the actor who played him has, sadly, passed away), and to feature another wedding.

We can only presume it will be Paris' wedding. I am writing this in late July 2023, and the movie has already been filmed (although delayed by the COVID-19 pandemic) and set to be released in September this year.

We shall soon see if my prediction comes true.

Cornetto

Short Answer: Road movie

This series is only barely one. Shaun of the Dead, Hot Fuzz, and World's End share no characters or plotlines, only a production team and a sense of humor. Yet, here we are.

They, respectively, parody zombie movies, buddy-cop movies, and sci-fi movies. So the logical thing is to keep going until they work through all the major genres.

So far, they have taken place in the present. So they could go for spy, superhero, kaiju, prison, road, or Die Hard-style movies (which have become their own subgenre. All of these are ripe for the type of knowing winks and physical violence that mark the Cornetto series, named for a British ice cream brand that appears in all the movies.

OK, so they share a production team, a sense of humor and... Good Humor. Or is that "Humour."

In any case, the necessity of including ice cream rules out some of the other action movie types they could skewer, like fantasy, Western, and war movies. 

I guess there could be ice cream in a war movie. Ice cream has been around almost as long as war, and this brand has been around since 1959. So that gives us all the wars since then to work with. Yay..?

Kaiju and superhero movies must be pricey with those special effects. Plus superhero parodies abound. Making fun of prisons is probably not cool anymore. 

Which narrows it to spy, road, and Die Hard. Again, there are as many Bond parodies as there are Bond movies. And the days of school and mass shootings make a Die Hard situation less funny.

So a road movie it is:

A guy has to move across England. He talks his friend into going with him and helping him unload and unpack at the far end: "I'll pay for the flight back."

He says they'll make it fun. They will stop in cool towns to sightsee and party. It'll be one last glorious road trip. The friend agrees.

Cue the Cornetto sense of humor and... action! References! Fights! Explosions! Gore! More references! etc. etc. 

They finally make it to the new place, with very little of his possessions intact, only to find more... plot to deal with. The promised roommate (or just mate) taps out, so the friend-- who wasn't doing anything anyway-- decides to stay as be the roommate. 

G. Marshall "Holiday" series

Short Answer: Father's Day

Only three things tie these movies together: they are set on holidays, they have intersecting rom-com storylines, and they have an embarrassment of A-list stars. 

Oh, and one more: They were all directed by Grary Marshall, a comedy legend best known for the sitcom Happy Days and its spin-offs, Laverne & Shirley and Mork & Mindy. For those of you who did not endure the '80s, that last one launched Robin Williams. 

His movies Valentine's Day, New Year's Eve, and Mother's Day are considered to form a trilogy, or at least a "trilogy."

Even though Marshall passed away in 2016, his formula could still work. So, which holiday next?

There are a billion Christmas movies, so having that holiday as the next one is out. Thanksgiving doesn't have many movies-- can you think of more than a handful?-- so it is a strong contender, even though there are umpteen TV episodes set on that day. 

Memorial Day and Veterans Day are hardly a setting for romantic comedies, and a Labor Day rom-com would be set in the world of... trade unions?

It would be hard to brand a movie Independence Day after the sci-fi blockbuster stamped that holiday as its own.

Which leaves Father's Day. Yes, there are movies about fathers aplenty, but this is a rom com, and how many of those about dads are there since... golly gee, the Courtship of Eddie's Father? 

Generally, the movies have four main plotlines that intersect so here are four for you:

1) A middle-age dad starting to date again, post-divorce, and its effect on his two kids, a 12-year-old and 15-year-old girl.

2) A granddad starting to date again, after the loss of his wife, and the effects of that on his grown sons, one who accepts it and one who cannot.

3) A couple with a teen girl who is just starting to date altogether. His mom accepts it... and her dad is freaking out.

4) A single mom trying to date again after a divorce, and having to keep in mind that she is not just looking for a husband for herself, but a dad for her kid.

The dad in 1 ends up with the mom in 4. The teen in 3 ends up getting inspired more by the granddad in 2, whom he takes cello lessons from. than his own dad; he dates the daughter in 1. 

Everything comes together at this major Father's Day picnic at the climax. There are old-fashioned games like a hoop-and-stick race, a sack race, and a "three-legged" race.