A couple more I thought of...
Password Plus-
Tony Randall zig zags his way down the steps, trying to upstage Marcia Wallace
Allen Ludden enters wearing Bowzer's jacket, which is much too small for him.
While not a funny entrance, once Betty White nearly stumbled down the steps during one opening, and I guess she was injured, because she was seated with her partner at the main area for the rest of the week.
During one week when Bill Cullen subbed, Greg Morris takes a seat at the host podium, but moves out of the way once Bill walks on.
Similarly, Gene Rayburn stood behind the host podium when Tom Kennedy took over for Allen. Tom allowed Gene to do the intro, but Gene realized too late that there was no mike on the podium, and gives Tom back his seat, explaining "I was getting a hernia shouting because there's no mike there!"
(I am guessing no one attempted to unseat Allen during his reign... somehow I don't think Allen would tolerate that)
Wheel of Fortune
Not really an entrance, but I do recall Pat Sajak modeling a car during one of the intros
Classic Concentration
Once, Margarie Goodson entered instead of Alex, explaining that Alex had gone too far with his ribbing of Margarie, and Alex was stuck modeling a boat that was shaped like a tractor, with Alex wearing a straw hat, trying to maneuver the boat. Margarie spares Alex further humiliation and gives Alex his job back.