Miranda Kerr -- Snapchat is More than Boobs and Penises (VIDEO)

Miranda Kerr wants you to know something about her boyfriend ... he did not create a boob app.

This is a super fun clip ... our photog -- a scrawny Aussie -- eased into the conversation by talking muscles and quickly moved to the subject of boobs, which he says is the staple of Snapchat.

Miranda, who's dating Evan Spiegel, begged to differ, but our photog then raised the penis.