How does Blue Teemo's ability work, specifically regarding the sequence of targeting and revealing cards, and can you play him from hidden with no valid targets?

Ruling: When Teemo's effect triggers, you choose targets first, then reveal cards with hidden to determine damage. You can play Teemo from hidden even if there are no valid targets since he is a unit; you just won't do the trigger.

Sequence:

• Choose targets when the effect triggers
• Reveal cards with hidden
• Split damage according to the number of cards with hidden revealed

Nuances:

• The exact number of targets (whether it's up to 5 targets or a single target) was not definitively resolved in this thread
• Whether "up to 5" can include 0 targets was questioned but not answered