Jamie Siminoff's first run as founder pitching his business on ABC's "Shark Tank" in 2013 wasn't what he'd hoped: He walked away empty-handed after rejecting what he saw as a weak offer from Kevin O'Leary. But Siminoff returned as a guest judge for season 10, because his company Ring went on to huge success — first billionaire Richard Branson became an investor and then Amazon bought Ring for $1 billion in February 2018.
"My pinnacle of success, I thought, was getting on the show as an entrepreneur. So to be able to come back as a Shark is a beyond surreal thing," Siminoff told CNBC Make It in October, when he returned to the show for the first time.
Siminoff, who was back in the Tank as a guest investor on Sunday's episode, also spilled "Shark Tank's" behind-the-scenes secrets to CNBC Make It.
When Siminoff pitched his WiFi enabled doorbell business Doorbot on "Shark Tank" — which he later rebranded to be home security system Ring — all the investors rejected him except O'Leary. Siminoff turned O'Leary down, but there was no bad blood when Siminoff showed up on set to be a guest investor. Still, the now multimillionaire did have some fun with the other judges.
"I definitely busted some chops, had some fun, because I earned it," Siminoff says. "I earned the ability to go in there and tell Kevin that he's not that smart, that he's not Mr. Wonderful. I told Mark that he didn't know what a tech company looks like...I really had fun with them."
It was all good-natured, though.
"The one that I talked to the most, which is what I think is the funniest thing ever, is Kevin O'Leary, " Siminoff says. "I really would say, even struck up a relationship with him. I had dinner with him one of the nights after taping... he's actually a great person. Great for entrepreneurship and for entrepreneurs, and business, and just a super fascinating person.
"We talked about wine," Siminoff adds. "He loves wine, and he likes cheap wine because he's kind of a cheap guy, so he was telling me kind of how to maximize your quality wine budget." (O'Leary, who owns O'Leary Fine Wines, gave CNBC Make It his secrets to picking a good wine for under $20 too.)
As a guest judge instead of a contestant, several elements of the show surprised Siminoff, who says he's been a fan of "Shark Tank" for years. He was impressed by the lucrative portfolios the judges have built from "Shark Tank" businesses — and that the Sharks really are investing their own money.
"It's real money, it's my actual cash, so I also want to make sure I'm doing the right thing," Siminoff says, and he knew things would move quickly.
"It's like a firing squad of information," Siminoff explains. "The entrepreneur comes out: 'I'm raising $600,000 for 12 percent of the company, blah, blah, blah,' and then they go into the whole thing. And people are firing questions, and you're trying to keep up with the knowledge because you are trying to figure out as quickly as possible, do I want this investment? If I want it, I need to act fast and I need to be definitive or else I'll be outbid."
He came prepared.
"I created a grid that had percentages on one side, money on the other side," Siminoff says. "So any time they would say, like, '$200,000 for 20 percent of the company,' I'd literally just sit there and [look] at the grid and circle it, for the valuation.
"And it's not because I can't do math," he adds. "It's because trying to even do that, I found, when everyone was talking, would get me out of the conversation of trying to be part of what was happening...so that was kind of like my little trick."
Siminoff says that now that he's been in the Sharks' shoes, he gets why he was rejected back in 2013.
"Now that I'm a shark, could someone have pitched us that I didn't invest in that is going to be the next biggest company on 'Shark Tank?' For sure," Siminoff says. "From that side, there's that realistic that there's just no way for anyone to tell."
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This story was originally published on Oct. 7 and has been updated. Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank."