I'm pretty much interested in the wall art, some signage, animatronics and the higher-end knick-knacks they made either for the redemption counter or for employee awards and gifts. Kind of a "I'll know I want it when I see it" thing. Don't worry about competing against me, though. If it's up on eBay, it's fair game.
I'd like to get a couple of the bots, but everything I said about the wall art goes double for them. The CEC bots are practically impossible to get, especially the full body ones currently used in stores. The parts are expensive so the company is keen to reuse any that get decommissioned when the stores close or are remodeled to the new "no robots" format. Most of the CEC bots owned by collectors are 1/2 body bots that came from franchised stores that closed back in the 80s. There's one up on eBay at the moment I wouldn't mind having, but it's local pickup only which is probably why it hasn't sold.
The Rock-afire Explosion bots are easier to find, but only by comparison. The company that made the RAE bots sold a few dozen shows to other restaurants in the 90s after breaking ties with ShowBiz. As those places closed, the bots sometimes came on the market so they occasionally show up for sale along with their various parts.
I don't collect costumes, but those are easier to find. Most of the ones that have come up recently are Cool Chuck, because they were in use for a long time and the company switched out walkaround costumes to the new look storewide in the last year or two. Employees were supposed to destroy the old ones, but some escaped onto the secondary market. Be prepared to fork out some cash, though. A complete Chuck walkaround with little to no damage runs approximately $800-$1,000 when they're available. Other characters pop up occasionally but are extremely rare.
The pride of my collection is actually a plushie. Bought it from a former corporate employee thinking it was one of the first known CEC dolls. They only had two stores when it was made and it has only popped up for sale three times in 15 years. Once I got it in the mail, it turned out to be a smaller version of the same doll, which no one knew even existed. Possibly a prototype that was never put into production. Pretty cool feeling knowing you've discovered something no one else has.
Anyway, if you are interested the CEC/SPP fan community board is here:
http://w11.zetaboards.com/Retro_Pizza_Zone/index/Accounts are activated manually so it takes a day or two after joining before you can post.