So, when you have a parent who adds this type of challenge to the scenario, usually the clothes are included in the deal. Specifically, if the kid's clothing gets stained/damaged/dirty in some way while they are with you, you have to deal with the resulting wrath of the challenging parent. I've been there and it's not pretty.
Our solution works for us. It may not work for you, but this is what we do.
CLOTHING: We usually have to travel between one hour and seven hours after we pick up the two kids, depending on where we're staying during the visitation. If it's midnight thirty when we pick them, up and they're sleeping, we don't worry about it. If there will be any eating, activity, or a drive longer than an hour, then we have them change clothes. We bring our clothes in a clear plastic zip-up bag, like the kind blankets and curtains come in when you buy them, and one or two sandwich sized ziploc baggies. It's labeled with masking on the outside "Clothing from _____'s House", so we know what it is. We pack clothes, shoes, socks, underwear, a brush, and a bottle of detangler (one of the girls has hair that needs it) in the bag. When we pick them up, we find a stop-off location and have the kids change over, putting their other shoes, clothing, etc. into the large clear bag. Any hairbows, jewelry, toys, etc. goes into the ziploc bags and put into the large clear bag so that they don't get lost. The large bag looks different enough to make sure we keep it accessible during the drop off change over.
Note: How long it takes for your child(ren) to change over depends on your family. I have one who's pretty quick and another that takes F-O-R-E-V-E-R and then dances in front of the mirror talking about how good she looks.
STUFF AND TOYS: If the kids bring stuff (or sneak stuff) from the other house, I generally have to put it away in a safe place to make sure it doesn't get lost. We are a relaxed household, and we share all the toys in our family when we're together. It's sometimes hard to explain to the kids that this toy belongs to another household and the parents there want to make sure it comes back in good shape, so they need to not play with it to ensure it's safety/location. It's particularly difficult for the child who brought it between the households because they brought it specifically to show the other kids and to play with it. I usually put the item(s) into a baggie or Wal-Mart bag and store it with the clothes for the return trip.
I know it probably sounds like the kids are heathens at my house, but they aren't and they rarely break anything. We have toys that have lasted six years, and they've been played with ALOT. The reality of the situation is that if you have a parent who is making the situation stressful, sometimes you have to be the better person and adjust accordingly to reduce the stress for yourself and the kid(s). It's not fair, but hey, we're the grownups (in theory) so we have to parent by example. Take the time to nicely explain that different households mean different rules and different stuff. We used it as an opportunity to talk about how people have different value systems, even within the same family. I mean you're parenting by example regardless, so you may as well do it right.