ZippyRedPlumber

You add the constant DOUBLEY ($80) to the third argument of the SPRITE command. It will make the MOB use two GRAM cards for a 8x16 sprite.

Not to be confused with the constants ZOOMY2 ($100) which makes each pixel in the MOB the same height as in BACKTAB cards, or ZOOMY4 ($200) and ZOOMY8 ($300) which makes them twice and four times the size of BACKTAB pixels. The naming comes from the fact that MOBs default to half the vertical pixel size than BACKTAB cards are.

Also make sure you are using an even GRAM number (0, 2, 4, 6, up to 62) for the graphic definition.