I don''t think peg in your sentence was used to mean "to classify or categorize".
Based on the full context:
Star Trek’s Captain Picard comes crashing down to Earth for his return to television.
One evening, as writer Jonathan Ames (of now-defunct HBO comedy series
Bored to Death) watched CNN, a thought occurred to him: Patrick
Stewart would look fascinating and striking behind one of these anchor
desks. Earlier in the year, Seth MacFarlane had approached Ames about
creating a show together, and MacFarlane had immediately suggested
getting Stewart on board. (Yes, that Patrick Stewart—of Star Trek and
stage-acting fame.) But it wasn’t until Ames pegged the actor for a
network news anchor that the show’s premise started to materialize.
And thus Walter Blunt, star of the new Starz show Blunt Talk, was
born. Blunt — a pseudonym Stewart often uses, taken from one of his
first roles with the Royal Shakespeare Company — is a fast-talking,
hard-drinking British network news anchor with a penchant for fucking
up. Within the show’s first 10 minutes, he’s stoned out of his mind
and reciting Hamlet on the roof of a police cruiser, right after being
caught “just talking” with a prostitute.
It is closer to mean:
6.To indicate or ascribe an attribute to. (Assumed to originate from the use of pegs or pins as markers on a bulletin board or a list.)
He's been pegged as a suspect. I pegged his weight at 165.
But it wasn’t until Ames pegged the actor for a network news anchor
that the show’s premise started to materialize. (quoted from Newsweek)
can be rephrased to:
But it wasn’t until Ames indicated the actor would be a good candidate for (a role of) a network news
anchor that the show’s premise started to materialize. (quoted from