My brother had watched the British version and hyped me up on the American version. The first episode I saw was the Booze Cruise in Season 2, which became really bizarre since Rob Riggle was on it, and I wound up meeting him while he was working for the Daily Show a few months later when he came to Texas to do a piece. That enabled me to become Chris Farley and say, "Hey, you remember that time you were on the Office? That was awesome."
It became the first "must-see" show for my wife and I when we started dating, We got married a few months before the Jim & Pam wedding, and I contend to this day that it should have been the series finale - Jim & Pam happy, Dwight has hooked up with one of Pam's friends, and the closing shot of MIchael going to bang Pam's mom is a great "fill in your own conclusion" moment.
While it wasn't as bad as Game of Thrones, they clearly had no idea what to do afterewards with the weird transition from the Will Ferrell cameo to what was a promising start with James Spader to limp-dick Andy Bernard in charge. Somewhere in there, I stopped being in front of the TV at the exact moment it came on every Thursday, probably when the British lady joined the cast - I'm sure she's funny in other stuff, but I found her just godawful. Then there was some sub-plot where some camera guy was in love with Pam and then some intern wanted to bang Jim? Angela married a gay politician who possibly slept with Oscar, and I really don't remember the rest. The finale was really nice, especially with Michael coming back, along with Ryan and Kelly, but after Carrell left it was just aimless wandering. Still a marvelous show that I have quoted, giffed, memed, for a couple of decades.
I had my kids - both 11 - watch a few clips of some of the safer humor and they loved it, particularly Dwight's snowball-geddon assault of Jim.