A lot of things can change during the development of a game. Half-Life is rich with lore, and because of this, things have constantly changed during the series development.
Articles related to Half-Life 2: Episode One
5 Intriguing Things BreenGrub Teaches Us About The Half-Life Saga

In 2012, Half-Life writer Marc Laidlaw began posting some strange things on Twitter under the name @BreenGrub.
It became apparent that he was giving us something. A brief history lesson involving Vortigaunts and the ‘Shu’ulathoi’ – the Advisor race of the Universal Union, through the mind of Dr. Breen, now transferred to a young Combine Advisor body.
Half-Life 2 Is 11 Years Old! Let’s Celebrate With a Stream Archive

Last year we embarked on a journey. Playing through Half-Life 2 and it’s episodes within a 24-Hour Live Stream. I crashed into invisible walls, took on the combine and got dominated in Half-Life 2: Deathmatch. Now a year later, we are unearthing the entire archive of the stream.
Half-Life and Portal Have Some Amazing Fancomics

Comics! Who doesn’t like comics? The Half-Life fanbase has created some fantastic material through the years. From 1998’s Walter’s World to the recent hit A Place in the West, we’ve compiled all of the creations that help document artists’ love for the Half-Life series. Maybe these can also help fill that Half-Life 3-shaped void in your soul.
Theory: Are Chell from Portal and Alyx Vance Sisters?

Fallout 4 has just been announced and there’s still no Half-Life 3 on the horizon. With no new content, fans have to create their own fun. Fan theories are an excellent way to revisit old material and put a new spin on it. So I present an hypothesis:
Chell and Alyx Vance might be related.
A Decade of Half-Life 2 – Live 24 Hour Playthrough

Happy 10th Birthday Half-Life 2!
It was today, November 16th 10 years ago in 2004 when Valve first released Half-Life 2 for the PC.
To celebrate, LambdaGeneration is hosting a live 24-hour playthrough of the game.
Community Spotlight: Kelly Bailey – Enemy #1

As a result of the recent public release of Steam Music, which also saw the release of the Half-Life and Portal soundtracks as free DLCs on the Steam Store, this week’s Community Spotlight features the work of DJ Anton Dubrovin (known online as “Thonidy”) who has created an awesome hour-long musical mix of the work of Kelly Bailey.
Community Spotlight: Half-Life 3: Awaiting Assignment

Whilst many of us have been waiting very patiently (or not so patiently) for news on the next Half-Life sequel, web designer Tom Bennet has been busy putting together a rather stunningly designed retrospective in celebration of Half-Life 2’s 10th anniversary.
Community Spotlight: City Numbered Seventeen

Thanks to Bury Shimel, also known as ‘KoreRat’ to the community, you can now follow Dr. Freeman’s endeavours on the social networking site Instagram.
Cat in the Hat Simulator: Valve and the Decline of Humor

This is an editorial by Lilgreenman which discusses the involvement of humour and comedic elements in Valve’s more recent games. All views expressed in this article are his own.
With all the noise Valve makes about Team Fortress 2 being “The world’s number 1 hat simulator”, their creative staff seem to have neglected a grounding in hat-based literature. Specifically, it seems they’ve never picked up a copy of the best selling hat-based book of all time (eat it, Oliver Sacks!), Dr. Seuss’ 1957 classic The Cat in the Hat.
Spoilers ahead for those who haven’t read C-I-T-H: The moral of the book is related to the two young protagonists by the titular feline, after he helps them clean up after a rowdy playtime session; “It’s fun to have fun, but you have to know how.” Which brings me, in my roundabout way, to my point. Valve’s top writers – internet comedy alumni Erik Wolpaw, Chet Faliszek and Jay Pinkerton – don’t seem to know how to have fun.