Cosgrove Hall wanted David Jason to play Ratty, but Jason preferred Mr Toad. Everyone who had voiced Toad had made him unpleasant, but Jason made him a lovable showoff. After he recorded an audition, he got the part.
David Jason got a letter from someone saying they saw a house on the market identical to Toad Hall three miles from Jason's house. Jason went looking for it and found it. He said it was wonderful and seemed to go on forever. It had a lake fed by its own spring. It wasn't Toad Hall, but he could imagine living in it. It was twice the value of the house he already owned. He thought about it but had to pay full price when he lost a coin toss (despite his reputation as a wheeler-dealer). But driving up to the house made him realize how much he wanted it.
The cast were surprised with the energy David Jason brought to Mr Toad and had to work to keep up with him. He claimed he just about held his own as Toad.