Here is a set of iMessage stickers that let you respond in good old "Internet Speak". Back before emojis, replies were abbreviated to a bunch of nonsensical words that were soon everywhere. This set includes
LOL
LULZ
LMFAO
BRB
FYI
MEH
PAW
OMG
and a whole lot more
There are also some bonus smileys rotated 90 degrees so they look as they should.