There's one other way to complete this puzzle that isn't mentioned in most walkthroughs:
1. Go back to Kennedy space center
2. In the museum, go to the third room, containing the "first monkey in space" exhibit
3. Wait about 30 seconds until the big hawaiian shirt guy and his family leaves
4. Pick up the taxidermied monkey
5. Go to Seaworld
6. On the screen to the left, pick up the electric eel from the aquarium and place it in the giant water flask you bought from the guy at the beach
7. Return to Disney World
8. Remove the eel from the water flask, and place it behind the guard's chair. He'll be distracted by the eel's thrashing about and start panicking about what to do
9. Use the taxidermied monkey with the fingerprint scanner. Your ticket will be marked as "validated"
10. When the commotion dies down, show your ticket to the guard, and he'll let you in
1. Go back to Kennedy space center
2. In the museum, go to the third room, containing the "first monkey in space" exhibit
3. Wait about 30 seconds until the big hawaiian shirt guy and his family leaves
4. Pick up the taxidermied monkey
5. Go to Seaworld
6. On the screen to the left, pick up the electric eel from the aquarium and place it in the giant water flask you bought from the guy at the beach
7. Return to Disney World
8. Remove the eel from the water flask, and place it behind the guard's chair. He'll be distracted by the eel's thrashing about and start panicking about what to do
9. Use the taxidermied monkey with the fingerprint scanner. Your ticket will be marked as "validated"
10. When the commotion dies down, show your ticket to the guard, and he'll let you in