Cramer's lightning round: I thought Luckin Coffee had peaked — 'I was dead wrong'

• It's that time again! "Mad Money" host Jim Cramer rings the lightning round bell, which means he's giving his answers to callers' stock questions at rapid speed.

Shake Shack: "I think Shake Shack had a really, really good quarter and the shack is back and I think it's O.K. to buy, although I have to tell you Wendy's is the cheapest burger company."

AGNC Investment: "I don't like that particular kind of REIT 'cause I don't know what they're in."

U.S. Bancorp: "I think that's a good one."

Luckin Coffee: "I don't deserve your blessing. ... I said this stock had peaked, and I was dead wrong."

ViacomCBS: "Viacom ... it's ridiculous, it's so low."

Disclosure: Cramer's charitable trust owns shares of ViacomCBS.

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