I’ve found another early appearance of ‘Lovecraft as character’. It was mentioned in the Bloch letters, and takes the form of a three-page spoof story/sketch. Robert Bloch’s humorous “The Ultimate Ultimatum” appeared in Fantasy Magazine for August 1935. This purported to be an account, over three pages, of a very large convention of writers and fans. Supposedly having taken place recently in a large crypt, the ‘event’ clearly anticipated the form of ‘the large science-fiction convention’ as it later emerged — none had actually happened at that point, though regional ‘conventions’ were a thing in amateur journalism.

The relevant issue of Fantasy Magazine is not online, and nor is the item itself, but here is a taster dug out of a later magazine article on Bloch…

It was a big convention. Lovecraft was there. So was Clark Ashton Smith, August Derleth, and Otto Binder. Ray Palmer was present, and Stanley Weinbaum. Also there was I, thrilled and proud at attending this gathering of masterminds.

In his letter to Bloch, Lovecraft commented on Bloch’s “The Shambler from the Stars” story in which he had also featured as a character. He added… “the spoof also is extremely clever — I can recognise myself except for the pipe”.

An endnote for the letter adds a little more text from “The Ultimate Ultimatum”…

Howard Cthulhu Lovecraft … sat in the corner, puffing furiously at a skull-shaped pipe.

So far as I can tell the spoof has never been collected, and the Fantasy Magazine for August 1935 has its only appearance. It’s unknown if there were illustrations, but probably there weren’t. It might make for an interesting 1960s Mad magazine -style comics adaptation, today, by a good caricaturist.