Whomever designed this spooge-flinging child's toy should probably be arrested immediately.
Unfortunately, "whoever" was the word the writer wanted.
Would you say "Him designed this ... toy?" Only if you were writing in the style of Tarzan, which is conceivable, given Defamer's Hollywood focus.
Hint: Use "whom" where you'd use him (or her).
Likewise, use who for he (or she). To recap: whom/him, who/he (me want Tarzan). The Ms stick together, as do the vowels.
Despite this, we still heart Defamer (and we think you'll be appalled by the toy).