Andersson, C. Dean, Fiend
T. T. Dysan is a mass murderer of children who goes to a comics convention in Texas where he knows many of his potential victims will be gathered. Also attending the convention is Joe Clark, there to sell his new comic book heroine Toxique. Both of them run up against Medea who is spending her immortality killing the murderers of children.
Resnick, Mike, "Harry, Larry, Barry & Frankie"
Three duck-shaped aliens arrive at the 2006 World Science Fiction Convention—L.A.con IV—with the intent of conquering the Earth. Frankie Thomas (a.k.a. Tom Corbett, Space Cadet) convinces them that they should all go out into space to save planets, right wrongs, and defeat evil. This takes place in an alternate universe where Frankie Thomas did not die before the convention. Contrary to what Craig Miller says in the story, these aliens are not minions of NESFA.*
*New England Science Fiction Association. There is some complex in-referring going on, and I am not privy. Frankie Thomas played Tom Corbett, Space Cadet in the 50s. He's one of those child stars who didn't transfer into being an adult star, says Wikipedia, which is tough on him, since he was 34 when playing TC, thought TC was in his teens. From 1979 to 2002, he wrote novels and stories featuring Sherlock Holmes. He went to loads of conventions, still fitting into his space cadet uniform. He was buried in it, aged 85.