Valki, God of Lies has a bug with double-faced cards. I specifically encountered this with Plargg, Dean of Chaos//Augusta, Dean of Order:

Step 1: Valki enters, exiles Plargg//Augusta
Step 2: Activate Valki, X >= 2, select Plargg//Augusta

Expected result: Valki copies Plargg (front face), and only the text/abilities on the front face are available/active.

Actual Result: Valki copies Plargg (front face), but also copies Augusta's (back face) static abilities, and then also incorrectly applies them to itself.

Unknown: I do not know if this also copies Augusta's triggered ability, as I did not attack while it was on the battlefield. I do not know if this bug is also in play with double-faced cards other than Plargg//Augusta, but some good candidate cards to check for the interaction would likely be Enduring Angel, Nicol Bolas the Ravager, and Valki itself.

Log at about a turn after Valki copied Plargg attached.