\startuseMPgraphic{smile}
    draw image (
        path p ; p := (0,2) .. (2,2) .. (0,-2) ;
        draw p randomized .5 ;
        draw (0.5,1) ;
        draw (0.5,-1) ;
    ) xsized EmWidth ;
\stopuseMPgraphic

\definesymbol[smile][\useMPgraphic{smile}]

\starttext

\startTEXpage[width=20em]

\dorecurse{100}{\dontleavehmode\symbol[smile] }

\stopTEXpage

\stoptext
