Shouldn't our weight advantage help us out more??

I just dressed a 21 month old who didn't want dressed. I think it was more the fact that he didn't want to go to bed and he expressed his frustration by refusing to have his PJs put on. Normally I can handle my kids even if they don't want to be dressed. However, this time I found it necessary to call in back-up. So here we are two grown adults both individually weighing significantly more than the 21 month old--and our combined weight really weighing more than the 21 month old--and yet we are still unable to get the kid's pants on him. Seriously, we tried around five times before I completely burst out in laughter. I kept thinking that our weight advantage should be helping us out more. You have to admire the kid's strength and stamina. Fortunately, we persevered and he was finally wearing pants. As Joe picked him up and began carrying him to his crib I said "Oh wait, shouldn't we change his shirt too?" You should have seen the look I got back...