Nitwits having fed creamy dessert to cats (8)

'nitwits' is the definition.
The definition and answer can be both people as well as being plural nouns.
Maybe there's a link between them I don't understand?

'fed creamy dessert to cats' is the wordplay.
'fed' means one lot of letters goes inside another (one word is 'fed' to another).
'creamy dessert' becomes 'fool' (I've seen this in another clue).
'to cats' becomes 'toms' (tom is a kind of cat).
'fool' placed into 'toms' is 'TOMFOOLS'.

'having' acts as a link.

Can you help me to learn more?