Q: What happens if Beam Us Up is played with the Teleporter/Transporter in play, and someone has a being/crew member with a Creeper attached to it on the table?

…Does the player with the Teleporter/Transporter get the Creeper as well, or does it stay behind with the player the Keeper was taken from?

A: The key point to understand is that what’s really happening on Beam Us Up, with or without the Teleporter/Tansporter in play, is that the Keeper AND Creeper are sucked up into one’s hand… and then the Creeper is rejected, since you can’t hold it in your hand, and it goes back down in front of you.

Once you think of the action as happening in that way, it’s clear how to arrive at the ruling: the player with the Teleporter gets the Creeper, since they theoretically sucked both cards up into their hand, and then their hand spat the Creeper out, as it were.

It would either then reattach to some other being/crew member if possible, or hang around for as long as it takes for a new Keeper of the right type to show up to attach to.

See: If someone plays Beam Us Up, and one player had a being/crew member with a Creeper attached, what happens?