Rat-a-tat-tat
Who is that?
Only Grandma's pussycat
What do you want?
A pint of milk
Where's your money?
In my pocket
Where's your pocket?
I forgot it
Oh! you silly pussy cat!

Cnagarnach (or is there another onomatopoeic word for it?)
Cé hé seo? or Cé atá ansin (?)
Tá ach puisín na mamó ann
Cad atá uait? or Cad atá tú a iarraidh? - (?)
Pionta bainne
Cá bhfuil do chuid airgid?
I mo phóca
Cá bhfuil do phóca?
Dhearmad mé é
A phuisín amadáin ós tusa!

Could I have your corrections please.

Cnag Cnag Cnag OR cnap cnap cnap (pronounced crap).
There could even be a better way to say it.
Cé atá ansin?
Níl ann ach puisín mhamó. OR Puisín mhamó anseo.
Cad atá uait?
Pionta bainne
Cá bhfuil do chuid airgid?
I mo phóca
Cá bhfuil do phóca?
Dhearmad mé é - I’m not sure if that is correct, personally I’d say Rinne mé dearmad air.
órú, A phuisín amaideach. (pronounced as "ara" in Connemara)

Go raibh maith agat - quite a few things seem so obvious once they've been corrected.