If I go into the Entralink to retrieve my items or catch Pokémon, then leave, do I need to save to keep the items/Pokémon? 
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Jonathan DrainDec 7 '12 at 4:58

Nope when you leave you'll need to wake up your pokemon to retrieve your items, if you don't wake him up the items will still be there waiting you to wake up the pokemon. 
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MichelDec 7 '12 at 12:16

I mean after you wake up your Pokémon and your items are sent to the Entralink, and you have to talk to the boy to the left of the exit at the top to retrieve them, and he calls them a remnant of your Pokémon's dream.  Do you have to save after that?  If you turn off instead, and go back to the Entralink, does the boy still have the items? 
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Jonathan DrainDec 7 '12 at 17:38

Just tested it: It doesn't save after you collect your dream items from the boy or leave Entralink.  If you restart without saving, your items will still be with the boy in the Entralink. 
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Jonathan DrainDec 8 '12 at 5:03