Roskoe, The Wild Sorcerer

Whenever you cast an instant or sorcery spell,
roll a d20.
1-9: Create a 0/1 blue Bubble creature token.
10-15: Add {u}, {r}, or {g} to your mana pool.
16-19: Deal 3 damage to target creature or player.
20: Copy the last instant or sorcery you played,
then cast the copy without paying it's mana cost.