I haven't seen any of the shows on TV, but I saw a clip on YouTube the other day that showed the end of a Final J! round. One of the answers (I think Ken's) was "Who is GHOST? (Greatest Host of Syndicated TV), Pat Saja Alex Trebek", and another (Brad's?) was "Ken es el hombre" or something like that. The third answer (James?) was the only serious answer. Alex made fun of the Pat Sajak answer, then commented that he wished Ken had lost more points, and then with the reveal of the second answer, turned to the camera and said "ladies and gentlemen, welcome to the Jeopardy comedy hour."
If this is anything to go by, it seems like these three have at least a decent rapport with Alex too. If that's how the rest of the shows have gone, it makes sense that it would be popular with viewers--it adds some genuine fun to what's normally a very serious and straight-laced show.