Thank you for the pics, muebe. That really looks tasty!
Ok WC you did a good job. Being a California boy I am very familiar with In-N-Out. Animal style is one of those secrets that are not listed on their menu but they will do. They also make animal style fries.
The difference I can see is they use two patties on the double-double burger that are much thinner than your one. So try grilling some thinner patties.
I believe they also grill the caramelized onions in mustard and it might not be the patty but I could be mistaken.
Layer your cheese in between and at the top/bottom of the patties.
I may need to get some In-N-Out for lunch today. If I do I will take some pictures of the animalized burger 
I guess it's not the onions that are grilled in mustard, because they say on their
website: "a mustard cooked beef patty"
Looks like the onions are between the two patties?
These animal style fries look like covered with the burger spread combined with melted cheese plus caramellized onions. Is that right? Is there mustard inside, too?
As far I understood the In-N-Out website you can get all burgers animal style, so my version is not the double cheese burger but might be an animalized cheeseburger...
