pattern - A funny game you can play with a friend of yours: brain reading

...but first you have to find the solution!

Two friends (Andrew and Gabriel) go to another friend (Ellen) and claim to be able to read each other's mind. Ellen doesn't believe that and wants to test their ability.

Andrew steps away from Gabriel and Ellen, gets blindfolded and waits. Meanwhile Ellen whispers something in the ear of Gabriel. Gabriel then says: "ok, let me estabilish the mental link, are you ready Andrew?" "Yes I am" replies the friend.

Then Gabriel begins to ask always with the same voice tone:

"Am I thinking of a fun park?" "Nope"

"Am I thinking of person?" "Nope"

"Am I thinking of Bavarian sky?" "Nope"

"Am I thinking of love?" "Nope"

"Am I thinking of a spider?" "Nope"

"Am I thinking of StackExchange?" "Nope"

"Am I thinking of a car?" "Nope"

"Am I thinking of a muzzle?" "Yes"

It was a muzzle. Ellen doesn't believe her ears and wants to test it again, this time to understand if it works both ways. After the same preparation, Andrew starts to ask:

"Am I thinking of playing soccer?" "Nope"

"Am I thinking of a fridge?" "Nope"

"Am I thinking of Ellen?" "Yes"

Ellen told Andrew exactly her name. She wanted then be sure that this wasn't a "turn based trick", therefore asked again Andrew to ask and Gabriel to reply.

"Am I thinking of Ellen again?" "Nope"

"Am I thinking of learning German?" "Nope"

"Am I thinking of the wild wild west?" "Nope"

"Maybe then I'm thinking of Will Smith!" "Nope"

"Are you sure? I may be thinking about a saloon then!" "Nope"

"I give you the solution, I'm thinking about an harpoon" "Don't make me laugh, you ruin my concentration! Of course not!"

"Ok, then am I thinking about a yellow Submarine?" "Nope"

"Am I thinking about a dirty table?" "Nope"

"Am I thinking about smoking a cigar?" "Yes"

Ellen becomes red with anger. They did it again! Andrew and Gabriel go on the entire day doing this game and eventually Ellen surprises them during another random day asking them to repeat the experiment. The number of questions always changes... Ellen asks if the trick is dependant on the number of questions or the day, but Andrew and Gabriel laugh and give Ellen a hint: "If it was a trick, which of course is not, it wouldn't be dependant on the number of questions or the day"

How did Andrew and Gabriel put this up?

P.s.: This has nothing to do with hidden microphones or something like that :)

P.p.s: If you DO realize how they did it, I will upvote you if you don't post the solution, but a list of questions/answers "Yes/Nope" to make other users go mad :D

Answer

Do these series work? If so, I know the answer.

Example 1

"Am I thinking about a raisin?" "Nope"
"Am I thinking about an ostrich?" "Nope"
"Am I thinking about a finger?" "Nope"
"Am I thinking about a moose?" "Nope"
"Am I thinking about an astronaut? "Yes"

Example 2

"Am I thinking about a snake?" "Nope"
"Am I thinking about the Eiffel Tower?" "Nope"

"Am I thinking about the Pacific ocean? "Yes"

Example 3

"Am I thinking about a traffic light?" "Nope"
"Am I thinking about a ring?" "Nope"
"Am I thinking about air?" "Nope"
"Am I thinking about a bed?" "Nope"
"Am I thinking about a bottle? "Yes"

Solution:

"A thing with 4 legs" is the key. The guess after the 4-legged item is the correct one.