Whiplash Trap — ruling 1

You may ignore a Trap's alternative cost condition and simply cast it for its normal mana cost. This is true even if its alternative cost condition has been met.

Whiplash Trap — ruling 2

Casting a Trap by paying its alternative cost doesn't change its mana cost or mana value. The only difference is the cost you actually pay.

Whiplash Trap — ruling 3

Effects that increase or reduce the cost to cast a Trap will apply to whichever cost you chose to pay.

Whiplash Trap — ruling 4

You must target two creatures as you cast Whiplash Trap. If you can't (because just one creature is on the battlefield, perhaps), you can't cast the spell.

Whiplash Trap — ruling 5

You can target any two creatures, not just ones that entered this turn.

Whiplash Trap : règles, fonctionnement et interactions (MTG)

Whiplash Trap 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

If an opponent had two or more creatures enter the battlefield under their control this turn, you may pay rather than pay this spell's mana cost. Return two target creatures to their owners' hands.

How it works : Whiplash Trap

Original English text — Wizards of the Coast / Scryfall

#1October 1, 2009· Wizards of the Coast
You may ignore a Trap's alternative cost condition and simply cast it for its normal mana cost. This is true even if its alternative cost condition has been met.
No other card is named in this ruling.
#2October 1, 2009· Wizards of the Coast
Casting a Trap by paying its alternative cost doesn't change its mana cost or mana value. The only difference is the cost you actually pay.
No other card is named in this ruling.
#3October 1, 2009· Wizards of the Coast
Effects that increase or reduce the cost to cast a Trap will apply to whichever cost you chose to pay.
No other card is named in this ruling.
#4October 1, 2009· Wizards of the Coast
You must target two creatures as you cast Whiplash Trap. If you can't (because just one creature is on the battlefield, perhaps), you can't cast the spell.
No other card is named in this ruling.
#5October 1, 2009· Wizards of the Coast
You can target any two creatures, not just ones that entered this turn.
No other card is named in this ruling.