Experiment Kraj has all activated abilities of each other creature with a +1/+1 counter on it.
{T}: Put a +1/+1 counter on target creature.
Activated abilities contain a colon. They’re generally written “[Cost]: [Effect].” Some keywords are activated abilities and will have colons in their reminder text.
Unlike with cards like Quicksilver Elemental, the costs of the activated abilities Experiment Kraj gains must be paid with the correct colors of mana.