Thicket Elemental
Creature — Elemental
Kicker 
(You may pay an additional as you cast this spell.)
When this creature enters, if it was kicked, you may reveal cards from the top of your library until you reveal a creature card. If you do, put that card onto the battlefield and shuffle all other cards revealed this way into your library.
Ron Spencer
Invasion (INV)
• #214Rulings
If you copy a kicked spell on the stack, the copy is also kicked. If the copied spell is a permanent spell, the token the copy of that spell becomes when it enters is also kicked.
(wotc • 2024-11-08)
If a spell's kicker cost was paid, the spell is "kicked."
(wotc • 2024-11-08)
If you put a permanent with a kicker ability onto the battlefield without casting it, you can't kick it.
(wotc • 2024-11-08)
If a card or token enters as a copy of a permanent, the new permanent isn't kicked, even if the original was.
(wotc • 2024-11-08)
The kicker ability doesn't let you pay a kicker cost more than once.
(wotc • 2024-11-08)
To determine a spell's total cost, start with the mana cost (or an alternative cost if another card's effect allows you to pay one instead), add any cost increases (such as kicker), then apply any cost reductions. The spell's mana value remains unchanged, no matter what the total cost to cast it was.
(wotc • 2024-11-08)
The "if you do" means "if you choose to reveal cards". You still shuffle if you have no creature card in your library.
(wotc • 2004-10-04)
Rulings
If you copy a kicked spell on the stack, the copy is also kicked. If the copied spell is a permanent spell, the token the copy of that spell becomes when it enters is also kicked.
(wotc • 2024-11-08)
If a spell's kicker cost was paid, the spell is "kicked."
(wotc • 2024-11-08)
If you put a permanent with a kicker ability onto the battlefield without casting it, you can't kick it.
(wotc • 2024-11-08)
If a card or token enters as a copy of a permanent, the new permanent isn't kicked, even if the original was.
(wotc • 2024-11-08)
The kicker ability doesn't let you pay a kicker cost more than once.
(wotc • 2024-11-08)
To determine a spell's total cost, start with the mana cost (or an alternative cost if another card's effect allows you to pay one instead), add any cost increases (such as kicker), then apply any cost reductions. The spell's mana value remains unchanged, no matter what the total cost to cast it was.
(wotc • 2024-11-08)
The "if you do" means "if you choose to reveal cards". You still shuffle if you have no creature card in your library.
(wotc • 2004-10-04)