it does not overwrite the other replacement effect , but instead adds on to it in this case
Once it resolves, it will remain in effect until the game ends, Ride the Shoopuf's leaves the battlefield, or some subsequent effect changes its characteristics, whichever comes first
But by tapping your summoning-sick creature, that high Crew cost that everyone assumed was equivalent to multiple creatures being tapped is much closer to you tapping one attacker to make a massive creature
Here's the breakdown based on confirmed spoilers: Emerald: Monsters Inc Mike Wazowski, James P
There are also cards like Feather, the Redeemed and Soulfire Grand Master that specifically mention instants, though those are branching into multicolor territory
(You may cast permanent cards from your graveyard by discarding a land card in addition to paying their other costs.) Legendary Creature - Treefolk Recursion (CTRL to add secondary) Removal Removal (CTRL to add secondary) Tokens Sapling Nursery Affinity for Forests (This spell costs less to cast for each Forest you control.) Landfall Whenever a land you control enters, create a 3/4 green Treefolk creature token with reach