Can you choose no targets with Teemo to avoid paying a Deflect cost, while still revealing the top 5 cards without dealing damage?

Ruling: If there is an enemy at Teemo's location, you must target it since Teemo's ability doesn't say "may" or "up to one". You cannot choose no targets to avoid paying Deflect costs.

Nuances:

• The question of what happens when you cannot or choose not to pay a Deflect cost on the only legal target remains unclear in this thread and may be clarified in updated targeting rules
• If Deflect costs can't be paid, the ability may fizzle, but this was not definitively resolved in the discussion