But technical hitches meant they had to stay on the ISS until now.
Amid scenes of weight-less joy, four replacements - from the US, Japan and Russia - finally docked in a SpaceX capsule, which is due to return Butch and Suni to the US later this week with two others.
Their crewmate Nick Hague wore an alien mask to greet the newcomers, who will familiarise themselves with the station before the handover.
The SpaceX capsule will undock from ...