Arthur Ransome’s characters have some out of date but still appealing ways to describe their own, or others’, stupidity. I had never heard ‘galoot’ before reading his children’s books, and quite like the combination with ‘mutton-headed’.
Use freely if you are looking for new ways to admit to stupidity, and here is a variant.
”We were a pair of mutton-headed galoots to go through the ice like that,’ said Nancy, hopping up and down.’
Source: Arthur Ransome, Winter Holiday (London: Vintage, 2012), p. 43