pip install requests giphypop

in xchat: /py load /path/to/xchat.py

then: /gif some words

click on a gif, bam.

To get this auto-loaded in xchat, stick a file in ~/.xchat2/ (YMMV on other platforms), call it something like gif.py, and make the contents:

__file__ = '/path/to/pygiphy/xchat.py'
execfile(__file__)