shat

It does make sense that it follows the pattern of sit and sat. My question is why doesn't 'fit' follow the same pattern? I can definitely see the relationship between 'fit' and 'fat'.

How about "shot"?

Wait...never mind.

"Falsely formed"? I think it sounds way better than shitted, don't you?

Supposedly, the past tense of shit, falsely formed on the model of sit and sat. But it's amusing nonetheless.