If you're reading this website, there's a very good chance Harold Ramis made a significant impact on your movie life.
Whether he was helping make Bill Murray a big screen star, or appearing in one of the films you've watched more than any other, Ramis' contribution to cinema should not be understated.
We've picked a handful of our favourites, but let us know in the comments what your favourite Harold Ramis film is.
Knocked Up (2007)
It might seem strange to include what's essentially a cameo in a list like this, but Ramis' brief contribution to Judd Apatow's pregnancy comedy is too special to ignore.
It's an incredibly natural performance - adding a layer of sweetness to what could have been a straightforwardly bawdy comedy. Rogen's character wouldn't have been anywhere near as likable without Ramis' (almost entirely improvised) presence.
"I love you. You're the best thing that ever happened to me." The level of simple sincerity with which Ramis delivers this line still gives us goosebumps.
It's almost impossible to believe that Ghostbusters is 30 years old, such is its continual relevance (even now, it's impossible to say 'Who you gonna call?' without someone bellowing back 'Ghostbusters!') - but it really has been in our lives for that long.
Generously giving Bill Murray most of the best lines (he co-wrote it with Aykroyd) whilst still saving some for himself, Ramis' perfect comic-timing and air of awesome weirdness made him our go-to Ghostbuster when we were doing impressions in the playground.
It's important to remember that this is an action-comedy flick in which none of the lead characters ever fall out.
They mock each other, sure. But there's no nastiness, no arguing, no real conflict within the group - just a bunch of mates doing a (preposterous) job together.
That's ridiculously rare, and is probably a huge part of why we all love it so much.
Through their (real) friendship, Murray, Aykroyd, and Ramis (with Hudson joining later) created a bunch of realistic friends who we all wanted to be mates with ourselves.
It's part of the reason there's been such an outpouring of emotion at today's tragic news - we feel like we've lost someone we all knew and cared about.
Ramis' directorial debut made an astonishing $40 million from a $6 million budget; not bad for a partly improvised flick shot over 11 weeks packed out with unproven movie stars.
Harold Ramis' eye for talent and willingness to take risks should be credited when considering Chevy Chase's and Bill Murray's subsequent successes; Ramis was arguably their most significant contributor in the early stages of their careers.
National Lampoon's Vacation (1983) / Animal House (1978)
We're cheating a bit here by having two in one, but it's impossible to separate Ramis' two National Lampoon hits.
Both were huge successes, and hugely influential. Animal House was released in '78, and you'd be hard-pressed to find a mainstream American comedy released in the '80s that wasn't at least partly influenced by it.
You can certainly see the mark it had on John Hughes, who Ramis teamed with on Vacation.
Groundhog Day (1993)
Perhaps the best use of Bill Murray in cinema history, Groundhog Day isn't so much a movie as it is a magic trick.
For for most films, a repetitive plot would be a criticism. Here, it's elevated to an art form - with Murray's weatherman Phil Connors forced to live the same day over and over until he learns a very important lesson.
As with Ghostbusters, Ramis co-wrote the finely-constructed screenplay. Unlike Ghostbusters, he also directed it.
The film was a financial success, making $70 million on a $14 million budget. But perhaps more significantly, it was designated a national film treasure by the Library of Congress after being selected by the National Film Preservation Board in 2006.
What's your favourite Harold Ramis movie? Tell us below.