Yes, nearly any creature can hop in the way and kill Combat Celebrant, but if there isnt a creature to do that work, the amount of damage being produced is utterly insane
If exerted be that through singing, questing, using one of their abilities or other reasons in another players turn these characters can be challenged, requiring the challenger to exert their own card and then resulting in both characters simultaneously applying their strength to their rivals willpower
Mikaeus, the Unhallowed Mikaeus, the Unhallowed gets its own slot separate from the other lords and undying creatures
If an effect causes a noncreature permanent to become a creature and sets its power and toughness as it does so, that creature will have that power and toughness
Tossing in spells that let you play extra lands per turn or search your library for extra lands to plop onto the battlefield (a speciality of green) means your hand is going to fill up real quick
The water billowing behind Pidgeot as it flies away is a nice subtle hint at how much of a fast and powerful flier this bird is