Samuel L Jackson & Stephen Merchant

I think he was joking.

~ "He was not a modest man. Contemplating suicide, he summoned a dragon." - Gothos

I think he genuinely didn't, to be honest. I could be wrong, of course.

If you think about it, it's not that unlikely. Jackson does an insane amount of things, this was 10 years ago for 5 minutes in a show that while critically acclaimed wasn't/isn't something that many Americans are familiar with -- and I'm guessing they had little interaction.

If you asked him if he remembered doing a bit part as himself in something with Ricky Gervais, I'll bet he'd remember that, but specifically remembering Merchant (whose face is not very well known at all in the U.S.)? Not necessarily, I'd say. Again my speculation, of course.

IMDb-boards would be less confusing if people would mark their signatures clearly.

It's hard to say but I'd guess he genuinely forgot. If I had the kind of career he's had over the last 10 years I doubt I'd remember the director of a weird sitcom I shot for a couple of days.