There are some variations of this, like:

Напугал кота сметаной

or

Напугал кота котлетой!

Means "trying to scare a cat with a piece of steak"

Also some other animals are involved to in the similar pattern and meaning:

Напугал кобеля буханкой

Above animals do like a food mentioned, but a hedgehog just doesn't care, isn't afraid of:

Напугал ежа голой жопой

Means "[you are] scaring a hedgehog with a bare ass"

other: напугал козла капустой

or

напугал козла огородом

and

напугал барана новыми воротоами

The same attitude can be expressed by a bit different but close analogue:

не так страшен черт, как его малюют

There are some variations of this, like:

Напугал кота сметаной

or

Напугал кота котлетой!

Means "trying to scare a cat with a piece of steak"

Also some other animals are involved to in the similar pattern and meaning:

Напугал кобеля буханкой

Above animals do like a food mentioned, but a hedgehog just doesn't care, isn't afraid of:

Напугал ежа голой жопой

Means "[you are] scaring a hedgehog with a bare ass"

other: напугал козла капустой

or

напугал козла огородом

and

напугал барана новыми воротами

The same attitude can be expressed by a bit different but close analogue:

не так страшен черт, как его малюют