I played in a short arc of Nobilis a while back. We had a good time.
We had a group of four, playing Nobilis of Christmas, Walls, Tomorrow, and the fourth I forget.
Our experience had nothing of Toon about it - it was a pretty serious, and fairly grounded arc.
I'm glad you had fun with it. As for it having or not having a Toon-like quality, here's a tidbit from the book:
Get the Deets! on...
This is a Power made of a cloud of dust with the body of a train and the head of a bear. She is drawn to malevolently violated contracts, including fictional contracts broken within the context of the game. By all rights Lirrane should be easy to avoid. Her movements are preceded by minutes or hours by the appearance of her track; at best, she has two choices of direction at any given time. However, her track lays itself out so inconspicuously that a person may stand or lay upon it for minutes or hours at a time without noticing its presence. Once Lirrane locates a contract-breaker, she pursues them without relenting; they can earn a few hours, days, or weeks of safety by getting off the tracks whenever they notice them underfoot, but sooner or later they will look up to see Adrimorphous bearing down on them. Proffer a stale scone drenched in lemon juice to Lirrane as the full fulfillment of any debts or obligations remaining to you under outstanding covenants and she will depart, never to trouble you again.
If anyone made it through that paragraph, congratulations, and apologies. If you love the idea of looking up the number of miracle points required to... summon a lemon-juice-drenched scone, Nobilis is the game for you. A multiverse of exceedingly random bits and bobs awaits!