The new implementation of cowsay in PHP does not take into account that the .cow files used by the original cowsay had escaped sequences within the cow.
See T9408#137497
Things which look like escape sequences should have their escape character removed during render.
_________
< oh dear >
---------
\
\
,__, | |
(oo)\| |___
(__)\| | )\_
| |_w | \
| | || *
Cower....