If Kato the Arm gives ganking to a unit, can they gank with him and be part of the same showdown?

Ruling: No, you cannot give ganking to another unit with Kato and have it move to the same showdown. Both Kato's ability and moving a unit to a battlefield you don't control open windows where you can't move units.

Nuances:

• Kato cannot target itself with its ability (day 0 errata clarifies "another friendly unit")
• This interaction has not been explicitly confirmed in official rulings, though the reasoning is based on game timing rules