When you cast a spell with replicate, you pay the replicate cost any number of times as an additional cost. The original spell goes on the stack as normal — it is only cast once. For each time you paid the replicate cost, a copy of that spell is created and placed on the stack (CR 706.10). These copies are not cast; they are simply put onto the stack.
Because the copies are not cast, they do not trigger abilities that care about spells being cast (such as 'whenever a player casts a spell'). However, they do trigger abilities that look for spells being put on the stack or that check for the number of spells on the stack (CR 706.10, 118.9).
The copies can be targeted independently if the spell has targets. Each copy is its own object on the stack with its own set of targets, and they resolve one at a time. The original spell also resolves separately.
Example: You cast Gigadrowse (which has replicate) and pay the replicate cost three times. One original Gigadrowse is cast and put on the stack, and three copies are created and placed on the stack — giving you four total objects on the stack, each tapping a target permanent.
This is governed by CR 706.10 (copies of spells) and the replicate keyword rule under CR 702.56, which specifies that paying the replicate cost one or more times creates that many copies of the spell.
Unofficial fan resource — not affiliated with or endorsed by Wizards of the Coast. Answers are AI-generated estimates grounded in the Comprehensive Rules and are not a substitute for an official judge. Verify anything match-critical.