I have heard a few different rules on this I thought it was for any child not wanting to ride. Last year while at MK CM told us at Space Mountain that the child had to be a baby or not tall enough to ride? Can anyone confirm what the rules really are?
Any child/person not able/wanting to ride that is unable to safely wait by themselves. So age, height, and disability would all be factors.
My niece age 5 was tall enough for TOT but she was afraid. We were given A swap without any issues.
Here's the official line from Disney: https://disneyworld.disney.go.com/guest-services/rider-switch/
With DS2, we had to bring him up to the CM so they could see why we needed the pass. Just something to keep in mind.
As with most of the rules at Disney, your mileage varies depending on the cast member. Most barely even glanced at my husband and son when I requested the lanyard. The actual process does differ pretty substantially from what is outlined online, but that's nothing surprising!
The "rules" also reference Frozen Ever After as offering Rider Swap, but no one has really been able to confirm if this is true. Especially since there is no height requirement on this one!
Do you just have to go to the CM at the entrance of the queue or does the other parent and non-rider have to stand in the queue and tell the CM just before entering the ride? I've read on the Mom's panel both ways but I can't imagine standing in some of those long queues with a baby or wondering toddler and no stroller only for them to find out they can't ride anyway.
You just go to the entrance with the non rider so the CM sees the non rider. The CM gives the other members of your party a lanyard and they enter the queue. The non rider party are then free to leave for some other activity. When the riding party gets close to the boarding area they exchange the lanyard for the rider swap. That is important...my brother did not realize he needed to do that and they came out with no rider swap for me to ride the first time he did it.