http://www.cbr.com/doctor-strange-alternate-stan-lee-cameo/
Gunn explained that he was “doing my pal Scott Derrickson a solid and shooting Stan Lee’s cameo for Doctor Strange at the same time I was shooting some stunt work with Zoe Saldana,” adding that he ran between the two sets, which were filming on the same soundstage.
In Gunn’s own words, Lee’s alternate takes involved:
Stan reading a book and leaning into the guy next to him, saying, “Do you know what excelsior means?”
Stan throwing his head back and laughing as hard as he can, yelling, “I’m laughing for no reason! I’m totally crazy!”
And, my favorite, Stan laughing hysterically at a Garfield book, hooting, “He HATES Mondays but he LOVES lasagna!” Supposedly that one was in the film for a while, but it ended up being too long for the scene.