I have changed the title to a more popular version. You have probably also seen (in ΛΚΝ):
Είπαμε, γριά, να κλάνεις κι όχι να το παρακάνεις. (I have added commas.)
There's a similar one (missing in ΛΚΝ): Είπαν στη γριά να κλάσει κι αυτή ξεκολλώθηκε or κι αυτή χέστηκε.
In more or less the same context as the similar proverb "είπαν της γριάς να χέσει κι αυτή έκατσε και ξεκωλώθηκε" which is rather less decent, and stronger in meaning because of the presence of χέζω (crap) and ξεκωλώνομαι (excessively tax the anus, to phrase it modestly), two words generally considered more improper than κλάνω (fart).
Both expressions imply that a concession is made to someone who by nature is somewhat lax in this matter (very old people frequently have difficulties in restraining the flow from said orifice) but the beneficiary is overdoing it because he/she has misinterpreted the concession or is knowingly taking advantage.
Edit: Κάθιδρος πάλι! Well, it was taxing and I'm not a fighter plane (in and out in a jiffy); just a lumbering bomber. :blush: