The actor's invitation came in the form of a caption on a throwback picture from the first day on the set of the action thriller.
Lutz stars as John Smilee, a former Navy SEAL recruited to help Barney track down Conrad Stonebanks, in the upcoming flick.
The third installment of The Expendables franchise finds the team in a conflict with Stonebanks, an arms dealer and The Expendables' co-founder, who is determined to destroy them.
Starring Sylvester Stallone, Jason Statham and Jet Li, The Expendables 3 hits theaters on August 15. This year's Comic-Con convention will be held at the Hard Rock Hotel in San Diego, Calif. from July 24 through the 27.