To summon a Pet, you need to have the Pet Whistle. 

Pet Whistle can be obtained while Run or bought in the Shop.  

While running, if you need to summon your chosen Pet, tap the screen twice and enjoy the wonderful ride. 

A pet can be summoned multiple times during a run. 

Summon duration 

Summon duration is the main quality of a Pet. It determines the length of time the pet is active after being summoned.  

Summon The Rarity of the Pet determines the duration.  Summon Duration can be upgraded with Coins.  

After a complete Pet upgrade, you will receive a Score Bonus. 

Score Bonus will work without having to select the Pet.