This is Spinal Tap. The cast does the commentary in character, as if they’d just discovered many years later that Rob Reiner was making fun of them rather than it being the serious documentary they thought it was. They spend the whole movie talking shit about him and it’s hilarious.

Anvil: the Story of Anvil. Such a touching movie by itself, the commentary by the director, a childhood friend of the band, adds more depth and pathos to the story. My wife and I watched the movie and then rewatched it immediately with the commentary even though it was past midnight and we would normally be in bed. The story is just that gripping.

Second the mention of Tropic Thunder made in another comment. RDJ improvising the whole commentary in character is amazing and will increase your estimation of him as an actor, if that’s even possible.

A lot of people consume content online where director’s commentary frequently isn’t present but I imagine there are still a lot of people who are into this niche.

This and deleted scenes are IMO the biggest loss with the shift to streaming.

I had the original run of Futurama on DVD and the commentaries were always interesting but there is no way I’m going to start hording physical media again.

The crazy thing is that its really just another audio track, from a technical perspective it would be at trivial to add to video stream but there must be additional licensing and they don’t seem to feel its worth the effort/cost.

I learned a lot about the production and design choices around Terminator 2 from the commentary – the totally legitimate digital copy I have has 2 tracks (one labeled just director and the other director & writer) and I think I remember most stuff from the one with the writer.

• James Cameron talks about paying for “digital winky removal” for the T-1000 intro scene and how he should see about getting a partial refund since they didn’t completely remove the nudity from Robert Patrick in the finished scene
• There’s talk about the difference/debate in how to handle removing objects in post; do you make them bright and obvious in production to make it easier to see/mask them out after, or try to blend them so if you miss portions in editing they are harder to see?
• Lots of little details like how they didn’t want any scenes of John Connor using firearms. It was ok if he handled them and helped with reloading etc. but they didn’t want to influence kids to think it was cool to shoot at people (it also works thematically with John not wanting to kill)

I haven’t checked it out but I’ve heard good things about the Cannibal! The Musical commentary track, IIRC they get progressively drunker throughout.

Here’s a bad one. After watching X-Men The Last Stand I thought it was so terrible that I wanted to know what the director (Brett Ratner) had to say about this crapsterpiece.

Among a lot of bad scenes, one that stood out to me was at the start of an assault, Ian MacKallen as Magneto tells Pyro something like “Wait. In chess the pawns go first”. Then they send in a bunch of useless mutants who get slaughtered. It pans back to Magneto and he says “That’s why in chess the pawns go first”. I thought, does the director think the audience is full of idiots? Did he really just have this famous actor repeat the same line within 3 minutes?

When it gets there in the director’s commentary, Ratner says something like “Yeah, we really had this academy award winning actor say the same thing twice.” He knew it was bad, and he still did it! Why? In general, I felt like his commentary was an insight into the mindset needed to make shitty movies.

Star Trek First Contact - Commentary from Director Jonathan Frakes (Commander Riker)

And, Invader Zim - Commentary by creator Jhonen Vasquez.

Both of these let you hear their passion for the work and learn a lot of interesting little things about the productions.