Not eating pellets shouldn’t cause gas, as pellets should be a minor part of the diet anyway. My rabbits get a tablespoon each of pellets a day. How many pellets are you giving him, and how old is he?

Just leave him with his portion of timothy pellets throughout the day, and don’t top it up with alfalfa ones. What is kaytee fiesta? If it’s a muesli mix, you really shouldn’t be giving that to him as, as you’ve seen, they pick out the bits they like (usually unhealthy) and leave other bits. If he is older than 6 months then he really only needs a small helping of timothy pellets everyday.

P.S. He’s adorable! All that fluff! 

I agree with S&L. It’s more likely the Kaytee Fiesta or possibly the celery that’s causing gas.
The kid pushing peas around on a plate is a perfect analogy. As long as he eats the pellets eventually, it’s fine. Buns are like kids, they want the bunny equivalents of French fries and icecream for dinner.

I agree about the adorability too =D

My bunnies actually see their Timothy pellets as treats ? they get so excited about them, I’m sure if you persist he’ll come round!

I recommend switching over to Oxbow myself – those are plain timothy-based pellets, nothing to distract the buns from eating what they should, and they’re what I feed my own two. They’ve been less wildly excited recently than they used to be, but in their case (as suggested on another thread when I commented on it), it’s likely “food security”, i.e., being confident enough in the stability of their daily food sources that they don’t have to go wild over them anymore (except for treats!)