Eternal Favorite is bugged. It lets you activate its second effect in the same chain link as the activation of the card itself, and it should not be able to do that.
https://duelingnexus.com/replay/4530ddf0-ba58-4d19-8380-963ca7394173
#Eternal Favorite
radiant latch
errant heron
Looks like an oversight when it was initially scripted, Ill pass it along.