1988:

SCRUB-A-DUB TUB

As the name suggests, this was a playset on a smaller scale and without any specific ponies to jack up the price. It had a lot of neat bathtime accessories, although this shower didn't spray real water. For some reason I have a feeling the pony featured on the box was Wave Runner from the 1989 Sunshine Pony set, whiich would imply this came out in very late 1988-9, but I can't be 100% sure I'm remembering correctly.

Though the insert calls it simply Pony Tub, by the time it hit stores, it did have the same name in the UK as North America, which was Scrub-a-Dub Tub.