Hidden Gibbons (ULG) from Urza's Legacy, available at 401 Games Canada.

• Rarity: Rare
• Finish: Normal
• Artist: Una Fricker
• Card Text:
  When one of your opponents successfully casts an instant or interrupt spell, if Hidden Gibbons is an enchantment, Hidden Gibbons becomes a 4/4 creature that counts as an Ape.