FASTPASS is available for several of Disneyland's more popular attractions, and is basically an advance reservation system which gives you a ticket to ride an attraction at a specific time. For example, you show up at Splash Mountain and obtain a paper FASTPASS ticket to come back during a one hour window later that day. The time of your ride "window" is printed on the FASTPASS itself, and may begin 35 minutes to several hours after you obtained the FASTPASS, depending on the crowds on the specific date of your visit. When you return at the specified time and present your FASTPASS ticket to the Disney personnel staffing the attraction, you will be allowed to enter a special line reserved for FASTPASS holders which allows you to board the attraction with minimal waiting.
There is no cost for FASTPASS, but in order to obtain one you have to walk to the attraction you wish to ride and insert the park admission ticket for each member of your group into the FASTPASS machine. At this point the machine will issue you the FASTPASS ticket(s). The system is set up so that you can normally only have one FASTPASS active at a time, unless the "return window" is more than two hours away. For example, you wouldn't be able to go to Splash Mountain and obtain a FASTPASS there, then immediately run to Space Mountain and obtain one there too. You would either need to wait until the "ride window" had begun at Splash Mountain before you could obtain the Space Mountain FASTPASS, or until two hours after you received your Splash Mountain FASTPASS, whichever comes first.
Note that you don't need to actually use the first FASTPASS before you obtain the second one. The "ride window" for the first FASTPASS just needs to have arrived, or two hours need to have passed, before you can obtain the second FASTPASS. Despite this rule, one "quirk" in the FASTPASS allows you to obtain a FASTPASS for one specific attraction even if you already hold an "active" FASTPASS elsewhere. This "FASTPASS-favored" attraction is Roger Rabbit's Car Toon Spin at Disneyland. Due to this quirk, you would be allowed to obtain a FASTPASS for Indiana Jones, for example, and then immediately obtain another one for Roger Rabbit.
The other important thing to note is that the FASTPASS systems between Disneyland and DCA are "disconnected" from one another. This allows you to obtain a FASTPASS at Disneyland, for example, and then walk over to DCA and immediately obtain another one there as well. Disney rarely, if ever, enforces the ending time printed on the FASTPASS. This allows you to use the FASTPASS at anytime after the printed beginning time as long as it's the same day.
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