Is No Time Like The Past going to be the first time TOS characters have interacted with one or more of the main characters from a 24th Century series in their own time?
Didn't TNG #32 "Requiem" have Picard thrown back to the time of "Arena"?
Yes, but he didn't interact with TOS characters, just with the Cestus III colonists.
's question, there's "Trials and Tribble-ations," of course. And Forgotten History