Magnum says that he escorted Robin Masters around the island to "scout locations" for his new book. In "The Case of the Red Faced Thespian" (S4), it is stated that Robin "never does research for his novels". Scouting novel locations is considered research.
I enjoy this episode allot, for many reasons, most of which have already been mentioned.
The quote (above) leaves me with a "quandry" though.....if TM personally escorted RM around the island, why would he still wonder if Higgins is actually RM? Only thing I have come up with so far is, Higgins could have hired an actor to play RM, but it would have served no purpose other than to convince TM that he (Higgins) is NOT RM.
There are other instances throughout the series that raise the same question/situation, like when TM has the hidden manuscript given to him by RM, etc.
So why until the very end, would TM still be wondering and asking if Higgins is actually RM? Not completely ruling it out, only suggesting that IF JQH IS actually RM, he went to very great lengths to cover it up on more than a few occasions.
I liked the light-heartedness of this episode, and as others have pointed out, seeing quite a number of series "regular" bit part players all assembed in the same story. I also was reminded of the Mad Mad Mad World movie, which is a hoot, to be sure. The same thought occurred to me concerning the Water Buffalo convention, and wondered if the writers were rubbing it in even deeper with the "reduce it to RUBBLE" comment........after all, what was Barney's last name
Anyway............very fun episode!