During a ranked match with a mage, which used Whizzbang’s random deck, my K’thir card turned into a Morphin Card , and stayed like that for the rest of the match.
Not a bug. Disguised K’thir reads
Each turn this is in your hand, transform into a random card in your opponent’s deck.
Every card in Whizbang’s Mage deck is a Morphing Card, so every turn the K’thir would transform into one of the copies of Morphing Card. If the Mage had shuffled a card into his deck (with, say Ignite
Deal 2 damage. Shuffle an Ignite into your deck that deals one more damage.
or Deck of Wonders
Shuffle 5 Scrolls into your deck. When drawn, cast a random spell.
or, for my Standard players, Adaptive Amalgam
Deathrattle: Shuffle this into your deck. It keeps any enchantments.
), then there would be a slight chance the K’thir would change into whichever card got shuffled in. But, since there’d only be one copy of that card, and 20 or so Morphing Cards, you’d likely still get stuck with the Morphing Card more often.
Edit: typo