Sleeper Dart — ruling 1

Sleeper Dart’s second ability doesn’t tap the creature. It can target any creature, tapped or untapped. If that creature is already untapped at the beginning of its controller’s next untap step, the effect won’t do anything.

Sleeper Dart : règles, fonctionnement et interactions (MTG)

Sleeper Dart is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

When this artifact enters, draw a card. , Sacrifice this artifact: Target creature doesn't untap during its controller's next untap step.

How it works : Sleeper Dart

Original English text — Wizards of the Coast / Scryfall

#1April 17, 2020· Wizards of the Coast
Sleeper Dart’s second ability doesn’t tap the creature. It can target any creature, tapped or untapped. If that creature is already untapped at the beginning of its controller’s next untap step, the effect won’t do anything.
No other card is named in this ruling.