As Hydradoodle enters, roll X six-sided dice. Hydradoodle enters with a number of +1/+1 counters on it equal to the total of those results.
Reach, trample
You can choose 0 as the value of X. However, you won't roll any dice as it enters and it will be a 0/0. Unless something else is raising its toughness, it will be put into its owner's graveyard.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.