3 Year Old Son Misbehaves When He Comes Back from His Father's...............

No matter what anybody says, little kids have a hard time going back and forth even if the parents still continue great communication. It's the transitions from one place to another, the getting used to one place and then having to leave to go somewhere else. It's not anything intentional on the child's part. They are just trying to adjust to things they don't understand.
This is sadly pretty typical and it's something you have to try to ride out in terms a small child can understand. He only sees his dad a couple times a month and little kids don't really have a concept of time or schedules at this point and hopefully, as time goes on, things will get easier.

Ugh, I am a child of divorce and my sister and I always had a hard time, coming back to "our" house.

Maybe dad could give his son a heads up during the afternoon that son will be heading back to "moms' house. He does not need to make a big deal out of it, but do a wind down of the time. "This afternoon at 4:00 we will start getting you ready to go back to your house with mom." It is 30 minutes, till you need to start putting away your toys. In 15 minutes, you need to make sure all of the toys are put away, so we can start your packing. "

Dad also needs to be careful with making a huge deal about "I will miss you so much." Instead say, I really enjoy seeing you. I will call you on Tuesday and Thursday.. or whatever is the scheduled phone calls..

I also agree about no 20 questions upon return, no mom and dad being catty with each other when son is returned.. And again a smooth transition. Dad telling son I love you. We will talk on the phone, skype.. whatever..

And mom welcome son with "so glad you are here. Do you want some time to play or to watch a video for a few minutes." Not a big deal with "I missed you so much,"

All of the over statements can overwhelm a child when they are already in the middle of their own transition.

The anxious, somewhat neurotic wind down period from going to and fro is a normal reaction. When he gets old enough to really understand the routine he wont act out much anymore. The transition is just an emotionally, confusing thing and he doesnt know how to let it flow out. Hopefully he isnt given the 20 question interview when he gets home. Nothing worse than making a kid have to dissect his visit and give a play by play. Mom should just give him a big hug and kiss and say "I'm sure glad you are home, did you have a fun time?".... and just leave it at that.

Normal. Mine are 10 and 12 and this year is the FIRST year they have come back and NOT acted weird!

In addition to Megan N ... I think there are too many parenting differences going on between mom and dad's house as well. the change from mom's way to dad' way may be hard for a 3yr old to grasp it is all about consistancy at this age.

With my step-daughter (she's 5) but since she was 3ish, I've been involved with her shared care. We've always split the week, so I'm sure emotions would be intensified when it's only fortnightly.
When she was about that age, if her routine was upset, she would cry and cry for the parent who had dropped her off until she was distracted by something.
As someone else said, suggest that the child be well informed about going back to Mum's house. I used to tell my step-daughter the night before that she would be going back to Mummy's tomorrow etc. so she didn't get any nasty surprises.
If the parents can get past their differences, that would make the world of a difference.
Also, she might need to put her foot down. Children need to feel like they can talk to their parents. I always discouraged my step daughter from acting naughty. I would try and get her to tell me what was upsetting her instead of just getting angry at her for being naughty.
It's okay for them to miss the parent they aren't with. I think alot of parents feel threatened and worry that their child loves/misses the other parent more. It's important that both parents acknowledge that the child is always going to be missing one of them. And children get different things from each of their parents. Maybe the father was the disciplinarian. I am in my house, and I know my husband would need to step it up a bit more if he wanted the same respect that I got. (In his defence, he's the cranky daddy when he needs to be).

Sorry if none of this helps, but maybe it will help someone else :)

Good luck to your friend.

All she can do is support the little guy and not take it personally. It's not about her it's about her son and how he's dealing with the change. Maybe it would be good for him to talk with someone about all the changes of his parents not being together...

Even aside from whether he sees his father too little or too much, the act of transitioning from one place to another is apt to elicit this type of behavior. I think verbally reminding the child on the way back in the car how exciting it will be to see the other parent (and sound like you mean it) and make sure you "listen to mom (or dad)" may help. This is so difficult for the child, his world has fallen apart, so think of that, and you will do the right thing.