(Strip Number 992, Original Publication Date, 17 December 1985)
Panel 1: As they walk to the car, we find that they've talked Mike into helping Jim with his luggage. Having found it to be heavy, Michael asks the old boy what's in it.
Panel 2: Jim's rather flippant way of telling him to mind his own business consists of him commenting on how he brought his iron underwear and wooden socks.
Panel 3: Not one to be deflected by being told to step off, Mike tells Lizzie not to believe that but instead believe that it's actually Christmas presents.
Panel 4: Since Lizzie still believes that Santa puts presents under the tree and dinner on the table, she asks Jim if he really has iron underwear.
Summary: Given that Jim is mildly gobsmacked and Marian is giggling behind her sleeve, we can guess where Elly got not having a clue as to how children think from.