Francisco Muniz IV, better known as Frankie Muniz, is an apparition that appears in Being Harley Quinn. He is based on the real-life famous child actor who, in the show, used to live next door to Harley Quinn when they were children.
He was Harley's first crush.
Frankie is seen wearing an ordinary T-shirt, jeans, and sneakers, with the addition of a black cloak with a hood when assisting Harley and her crew in her mind. He has reddish-brown hair, greenish eyes, and his front teeth appear slightly longer than the rest on his poster in younger Harley's bedroom, although the latter trait doesn't seem the same in Harley's mind.
Frankie was a child living in the same neighborhood as a young Harleen Quinzel, who developed an unhealthily obsessive crush over him to which he unrequited, going as far as to file a restraining order over young Harleen's stalking. He appears in her mind to help them as a Deus Ex Machina before they are completely overrun by the Harley Gremlins and leads them to the emergency exit they had been looking for. He claimed that he was looking back at Harley whenever she looked at the poster of him she had on her bedroom wall.
Almost nothing is shown of the real Frankie's personality outside of Harley's mind but it can be assumed he was scared and concerned about Harley's stalking of him, seeing as she received notice of him filing a restraining order against her. In Harley's mind, Frankie addresses her calmly and friendly, not even dropping the smile on his face when Harley discussed her childhood plan to get pregnant with his child. He goes out of his way to be massively helpful to Harley and her crew, saving them from their deaths by leading them to the emergency exit they had been searching for.