Sylvester McCoy (in-universe)

Sylvester McCoy was an actor who portrayed "Doctor Who" in a television programme of the same name, and was considered by the Twelfth Doctor to be one of the greatest actors on Earth. He was brought together, along with many other actors to portray "Doctor Who", for a special breakfast in "London's glittering West End". The Twelfth Doctor considered making an appearance, to "see what these fictions [were] like." (WC: Peter Capaldi and Simon the Shy Cyberman Invite You to Breakfast with 7 Doctors)

He appeared on the front cover of a Doctor Who Season 24 boxset which the Seventh Doctor gave Melanie Bush. Here, he appeared similar to the Seventh Doctor. (WC: 24 Carat)

Information from non-valid sources
In 1993, he and his fellow living Doctor actors got into an argument over the size of Tom Baker's "part" in The Dark Dimension, which ultimately led to its cancellation. (COMIC: Doctor Whoah! 379)

In October 2007, he dressed up as the Fifth Doctor in an attempt to infiltrate the rehearsals for that years Children in Need special. (COMIC: Doctor Whoah! 388)

Other matters
Evidently, "Sylvester McCoy" here was intended to be an in-universe version of the real Sylvester McCoy, who portrayed the Seventh Doctor. The end of WC: Peter Capaldi and Simon the Shy Cyberman Invite You to Breakfast with 7 Doctors included a screen featuring photographs of each Doctor who would be present at the event, in-costume as "the Doctor". If taken as an in-universe representation of McCoy, this qualifies as one of the only in-universe illustrations of the character outside of parodies, along with an appearance on the front cover of Doctor Who Season 24 in WC: 24 Carat.