Hey Arnold! is one of many older shows that have recently reeled back in their now-grown audiences with a reboot. In 2017, its long-awaited, arc-closing one-off sequel movie, Hey Arnold: The Jungle Movie, released to acclaim, and is currently streaming on Netflix and Hulu.
The very existence of such stirred a renewal of interest in the 90s Nickelodeon staple that prided itself on authentically capturing child life on a realistic, simply-animated level. Those flocking to Hulu to stream the original series in its entirety will learn upon reunion with their beloved show that it featured much more star-power—albeit in a guest capacity—than their young minds initially realized.
Harvey Korman
Many Hey Arnold! diehards will easily be able to recall the Frank Sinatra-inspired crooner within the show's expansive universe, "Dino Spumoni." Full-blown aficionados may even the arc depicted within episodes like "Partners" and "Dino Checks Out," where his love/hate rivalry with his songwriter and music partner, Don Reynolds, was explored in great detail.
But, even they may not have known that the latter was voiced by Harvey Korman, most known for his work on The Carol Burnett Show and in several Mel Brooks films.
Daniel Stern
The "Back to School" when Arnold's Grandpa returns to grade school to complete his education.
A star of several other hit comedy films of the 90s like City Slickers and Rookie of the Year, Stern also notably provided the narration for The Wonder Years (1988-1993), a similar coming-of-age half-hour comedy that Hey Arnold! has drawn comparisons to on several occasions.
Jean Smart
As one-half of Helga's best friend Phoebe's mixed-race parental tandem, Jean Smart (Frasier) offered a familiar voice for the parents watching Hey Arnold! over their kids' shoulders.
Though she only participated in one episode, it was enough to make a lasting impression on the now-grown-up Hey Arnold! viewer who is just realizing in hindsight that Phoebe's mom was voiced by none other than Laurie Blake from HBO's Watchmen (2019).
Davy Jones
It would not have been high-caliber, half-hour TV if The Brady Bunch at the peak of his TV-turned-real band's fame, Davy Jones and his mates would follow up the occasional, brief reunions over the years by appearing together on scripted programs and performing.
Notably, they used such opportunities to sing covers rather than originals. In a 1995 episode of Boy Meets World, they sang "My Girl" by The Temptations. And, in 2002's "Fishing Trip" episode of Hey Arnold!, they sang the "Miss Susie Had a Tugboat" schoolyard rhyme as per Harold's request.
Andy Dick
His three-pronged credo: Protect the weak and downtrodden, serve for the good of all, and be kind to all creatures. His voice actor: Andy Dick.
Today, no one catching the season five episode that first cast a light on the local vigilante's backstory could mistake his distinct voice with anyone else's but the aforementioned comedian's. With the ultimately super-heroic Monkeyman's polarizing reputation among the townsfolk mirroring the controversy surrounding Dick's behavior in real life, the two have seemingly become a match made in Banana Heaven. Monkeyman!
Elliot Gould
"Today, I am a man." One thing Craig Bartlett's groundbreaking series did better than anyone was humanize its running slew of bullies and antagonists in episodes devoted solely to their individual exploits when not clashing heads with the rest of the gang.
Case in point being Harold's Jewish heritage, as depicted in both "Harold the Butcher" and "Harold's Bar Mitzvah." Under Rabbi Goldberg, Friends), Harold learned that stealing was wrong while also embracing his religion enough to overcome initial nervousness related to reading from the Torah at his Bar Mitzvah ceremony.
Ron Perlman
Surely the only player to have faced Bob Gibson in the 1960s to still be playing by the time the mid-90s rolled around, Mickey Kaline retired back on top, overcoming an embarrassing slump to muster up one last home run, which Arnold caught and returned to him after the game.
The fictional Hillwood Black Sox slugger is as rich as they come within the Hey Arnold! lore. His amalgamated namesake combined two famous Hall of Fame ballplayers: Drive), made for the deadliest dead-pull hitter animated Downtown Brooklyn ever did see.
George Takei
Yet another noted veteran actor whose voice is instantly recognizable, George Takei and his performance as Phoebe's Japanese-American father Kyo Heyerdahl would have most likely gone over the head of younger demographic viewers at the time.
However, a couple of decades later, there are many rewatching who will retroactively jump with excitement upon realizing the Star Trek alum lent his voice to the show. In doing so, he became the first fluently-speaking Japanese character introduced in Hey Arnold!, a show long-praised for its early arrival in the field of diversity representation.
Julia Louis-Dreyfus
Though Arnold was always known as one prone to falling head-over-heels in love with a different crush nearly every season, "Crush on Teacher" was, as the title reveals, the first time he dealt with having feelings for an unattainable adult character.
Moreover, his substitute teacher Miss Felter, who so happened to have a fiance bearing Arnold's same name, leading to Seinfeld days were winding down.
Lou Rawls
Since he was assuredly more known for music than acting, many kids and parents of the 90s alike may have overlooked Lou Rawls' performance as Harvey the Mailman in quite a few episodes of Hey Arnold!
The three-time Grammy-winning singer of "You'll Never Find Another Love like Mine" memorably offered up an anecdote to Gerald in "Gerald's Tonsils" that helped cheer him up. Harvey recounted how his voice changed just before singing in a school concert, suggesting his character may have once had vocal skills similar to the real-life Rawls'. Regardless of how skilled Rawls' in-universe character may have been at singing, one fact remains certain: he could never hold a candle to the Sunset Arms Boarding Houses' resident country star, Mr. Hyunh.