While “Skill Drain” is active, you can’t put new counters on “Balloon Lizard”.
The counters on “Balloon Lizard” are different from Spell Counters.
Remove all counters on “Balloon Lizard” if it is flipped face-down or removed from the field.
You can use “Barrel Behind the Door” against “Balloon Lizard”’s effect.
“Balloon Lizard”’s effect activates when it is sent to the Graveyard after being destroyed.
Netrep Rulings:
If “Skill Drain” is active, “Balloon Lizard” will not receive any counters for as long as “Skill Drain” is active. “Balloon Lizard” will lose any counters it had when “Skill Drain” is activated.