The Egyptian-born Canadian newcomer was thrilled to finally come face-to-face with Will as they prepared for the live-action Disney film, but in his nervous excitement, he ended up embarrassing himself.
"I was on set and it was still prep (in the preparation stage) so... I was in dance rehearsal and I was waiting for this day. I was like, 'Oh, Will's here, I gotta go up and say hi...,' " he recalled on U.S. show "Live with Kelly and Ryan".
The "Men in Black" superstar had been in conversation with director Guy Ritchie when Mena strolled over.
"He (Will) was in the gym and he was talking to Guy Ritchie and I was like, 'OK, Guy will help break the ice and I'll just show up and say hi.' So I went up, I was like, 'Hey, hey Will. Hi!' "
"He was like, 'Hi!' and I walked away like, 'I did not tell him who I was...!' He thought I was one of the dancers, I think, 'cause I was in my dance gear."
Mena decided a redo was in order, and this time around, he was given a warm welcome by Will after realising the young actor was actually playing the titular character.
"I was like, 'OK, I gotta go back,'" Mena shared, "and I was like, 'Hey Will, it's Mena,' and he was like, 'Oh, hey Mena, what's up?'"
"So I missed the boat on that one the first time. It's Will Smith, you know?"
Smith portrays the Genie in the "Aladdin" revamp, alongside actress Naomi Scott as Princess Jasmine.
The movie opens in theatres later this month.