Collection delay is a trick that delays or prevents Link from picking up an item when he is supposed to collect it. This can be done for any item that Link would hold over his head when he comes within range of it on the ground. Additionally, when receiving an item from an NPC, a collection zone appears around the NPC when the dialogue ends that causes Link to perform the animation and collect the item. This zone works exactly like picking an item off the ground, although it is much larger and invisible. The radius extends a certain distance from the NPC, and is different for various NPCs.
Certain actions take priority over collecting an item, and can be used to pass right through a collection zone without interacting with it.
Navi-targeting while in an NPC collection zone will prevent Link from collecting the item. Additionally, these actions will prevent collecting an item:
When collecting an item from an NPC, the collection zone should typically take effect the instant the dialogue ends. This means there's no time to do any other actions before Link collects the item. For certain sequences however, it will take one extra frame for the collection zone to appear. This gives the player one frame of input after the dialogue ends, which can be used to perform an action. This is commonly done when pressing B repeatedly to end a dialogue, and accidentally drawing the sword. Both navi-targeting and pivoting take two frames, so they can't be used.
NPC interactions which have a natural collection delay frame include:
† These natural collection delays were removed in v1.2
Holding Z after Link resets his state from certain animations will store a collection delay effect. This can be used to walk right over dropped items without picking them up until releasing the Z button. Similarly, storing the effect and then talking to an NPC will cause the collection zone to take two frames to appear when the dialogue ends. This gives the player two frames of input to perform an action.
To store a camera collection delay, hold Z during one of these animations:
After storing a collection delay, releasing Z, backflipping, sidehopping, falling off a ledge, taking damage(?), and certain other animations will cancel the effect.
Due to a weird property of Navi-targeting, it's possible to automatically target an object by holding Z before walking up and talking to it, and then holding Z when the dialogue ends. Because targeting takes two frames, combining this with camera collection delay will cause Navi to target the NPC when the conversation ends, simply by holding Z. This doesn't work on certain NPCs, however.
When entering an area, white text will fade on screen indicating the title of the area you are in. While this text is on screen, Link will not collect items. This is common in shops, where the player quickly buys an item, and then walks away before collecting it.
While Down A (or Blank A?) is active, Link will not be able to hold items over his head. This works for NPCs as well.
After performing the empty bomb glitch, the game will still think Link's hands are full, and he won't be able to receive items. Although it is still possible to talk to NPCs in this state, the item won't be collected until the glitch is canceled.
Sometimes dropping a fish before a dialogue will cancel out the collection zone. This likely has to do with the fish having its own collection radius to determine whether Link is close enough to catch it. Usually Link has to be practically touching the fish for this to work. Sometimes it only works if you drop the fish after the dialogue. Might only work with NPCs and not dropped items. This should be looked into...
Talking to the cucco lady as child (others?) at the same time you leave her talk range will cause one frame of collection delay...
While standing in a collection zone, the action icon changes to "Grab" or "Open", although pressing A won't do anything.
When receiving the purple rupee from the cucco lady as child, any delay at all will completely cancel the collection altogether, and she will return to normal as though she had given it to you.
Certain NPCs use a flag to determine which item they should give you. In some cases this flag is cleared one frame after the dialogue ends, which means any extra delay will cause Link to receive the wrong item. Although this applies to King Zora, he was patched on v1.2, and the flag is no longer cleared when the dialogue ends.
When receiving the Biggoron's Sword from biggoron, any delay will cause him to not give you the sword. However, the BGS flag will still be set, and the icon for the sword will be shown in the inventory. Since biggoron has a natural colelction delay frame, this can be done easily on accident. Since the BGS flag is set, he will no longer offer the sword, however buying the Giant's Knife will act like Link received the BGS instead. This was patched on v1.2, and the BGS flag is no longer set when the dialogue ends.
Bringing up a text box during a collection delay in a shop will softlock the game, likely because the shopkeeper normally asks what else you want to buy after you receive the item.
Collection delay can be used to dupe over a trade item after trading it, and then collecting the item to do Trade Item Duplication.
Delaying collection from King Zora can be used to receive the Eyeball Frog instead of the Zora Tunic, or the Zora tunic instead of the Eyeball Frog, but only on v1.0 or v1.1. It can also be used to receive the Gold Scale from the fishing pond guy instead of the heart piece.