"He started talking to our keyboard player, … and I just assumed these guys knew each other," said Thompkins, noting that the two were laughing and seemed like good friends. "I didn't realize it was Belushi at all."
Then, Belushi came over and introduced himself.
"He comes over and looks at me and says, 'Hi, I'm Jim Belushi,' and I'm like, 'Really?'" Thompkins said.
The "Saturday Night Live" alum is starring in local filmmaker Matt Porterfield's fourth feature film, "Sollers Point," which was scheduled to start filming here in Baltimore at the end of last month.
After learning that Belushi had his harmonicas with him, Thompkins asked Belushi to join him on stage.
He announced Belushi as one of the "great American actors," and then Belushi and the band played for about 15 minutes, Thompkins said, including a song by Junior Wells, "Messin' with the Kid." The restaurant was packed within minutes, Thompkins said.
"He was great," said Thompkins, who said he almost forgot that Belushi made music.