After the family listens to the race where Herman's horse "Bluebell" wins, Eddie turns the radio off by turning the knob clockwise. Radio knobs are always turned off by turning the knob counter-clockwise.
It's obvious there's another person dressed as Herman when he is hanging from the flagpole and standing on the ledge when the flower pot falls.
After opening one of the doors to the room's entrance, Herman spots a henchman guarding the room in the outside hallway. Herman reconsiders his escape route and begins to shut the door. Just before the door closes a hand from one of the crew hidden on the other side of the door enters the frame, apparently reaching out to give Fred Gwynne assistance with the door. The hand pulls back when the person realizes their help is not needed and Gwynne closes the door.
As Grandpa is flying away after giving Herman his anti-gravity pill, the rod holding the bat is visible in the upper right-hand corner.
Just as Grandpa (in bat form) says goodbye to Herman and flies away from the ledge, you can see a pole in the top right used to control the bat.