Aside from occasionally saying rats(yes this is a swear in a series of books I read), I mainly just replace any curse with bullocks.
"What the bullocks are you talking about?"
"Where the bullocks is my slinky?"
"BULLOCKS!"
And then on.
"What the bullocks are you talking about?"
"Where the bullocks is my slinky?"
"BULLOCKS!"
And then on.