S3·E25 Lovespell from the Underworld

Martin is reunited with his first crush, Vivian Michelle, who embarrassed him during the grade school times. Martin tries to avoid her, but when he finds out that Vivian has changed, he changes his mind about her. Diana suspects that Vivian is different due to her strange skin. Vivian is actually Venoso, a mutated chameleon who was the first monster Martin ever caught, out for revenge.