Can you play a unit into a showdown using an effect like Get Excited discarding Flame Chompers when the battlefield is being attacked?

Ruling: Yes, you can play a unit into a showdown on a battlefield you control. The battlefield remains under your control until the showdown finishes, so playing a unit there (such as through Get Excited discarding Flame Chompers) is legal.

Nuances:

• The battlefield does not become contested until after the showdown resolves
• You can also play units to a battlefield you control that has no units on it