I hope it doesn't give him "gas".

Well, I guess he's getting his fiber!  Maybe he has a flair for
international cuisine??  And, the results can't be any worse than
mouse-breath/farts.
Cats often eat grass and other greenery to aid in digestion.  I think
most cats instinctively know what's good and what's bad for them, so I
wouldn't worry too much. Moderation is probably best practice, so I
wouldn't load the old boy up on the stuff.
Also, I know that my cat sometimes eats wacky stuff just for a change
(or maybe just to show off???), but it's usually just a short love
affair with said food.  Fickle girl, she is!

Garlic is not that good for cats. Related to onion. The rabe is probably
fine though.

Some cats will surprise you, with what they like. ;-) A friend's cat
liked peas & corn.  Go figure.  One of my cats liked cantaloupe.

Besides chocolate, onion & garlic aren't good for cats, although the
amount of garlic he's eaten as an addition to the broccoli probably
isn't enough to worry about. .  Don't know about hot peppers... ;-)

Cathy

That's wild!

Nothing wrong with veggies.  However, I wouldn't give veggies that
contain hot pepper in case he gets a stomach upset.  There are
differing opinions about feeding garlic to cats.  If they are fed
garlic on a regular basis, they could become suseptible to anemia.
Onions are more of a danger for cats so I'd definitely steer clear of
them.   I feed my cats a homemade diet and they get a small amount of
veggies that are put through a food processor.  They also get some
cooked squash which is a good source of fiber.

Lauren