Professor Schwartzman's Acme Canine Decoder 2000
Retina, 24 18 17 16 bytes

1 byte saved based on an idea in MT0's answer.

\wf?k?
y
\byy
He


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Explanation

\wf?k?
y


This simply turns all letters into y, but if they are followed by an f or k we immediately replace that as well. By removing f and k we "normalise" the lengths of the words so that they now all have two more ys than they need.

\byy
He


This turns the first two y of every word into He, completing the transformation.