It seems to be grafted - see where the rootstock was cut? Rootstock is different, and usually faster growing plant.

You've got a crested Cliestocactus winteri aka Golden Rat Tail cactus grafted to a Hylocereus:). That crested cactus looks really nice when it gets big:).

Thank you Rina, that’s what I originally thought but then he was talking about a mother plant, which threw me. I’m guessing they must have a large grafted cactus and then a bunch of small.

Kara, you did it again! You’re amazing! Thank you! When my friend asked what it could be I told him there was someone on gardenweb who might know and that you were our best chance. Haha. Thanks again!