There is a line from the film Dreamcatcher, spoken by Pete.
Motherfucker tried to bite my dick off, Jonesy. I always thought it'd be my ex-wife did that.
It sounds jarringly ungrammatical to me, even for informal speech. I understand it means "I always thought it'd be my ex-wife that was going to do it." Is this way of speaking common? And am I right to say it is ungrammatical?