In today's strip, Deanna discovers that one of the things 'cleverly' stored in the crawlspace was Grandma Marian's wedding dress. Mike says that he had no idea that Elly had it. My guess is that Elly didn't know either or else she'd never have shut up about it and insisted Deanna wear it. When Jim hid it, he did something odd and kept his mouth shut. Mike asks Deanna what to do with it, is told it's a heirloom and says "put it back in the crawlspace" like the idiot he is. It's not as if he has a kid sister who might like to wear it at her wedding or anything, after all.