The first appearance and original origin of Detective Chimp

Detective Chimp first appeared in a seven-and-a-half-page back-up strip in 1952's The Adventures of Rex the Wonder Dog #4, the work of writer John Broome, pencil artist Carmine Infantino and inker Sy Barry. That short story was entitled, simply enough, "Meet Detective Chimp!" and was thus devoted to introducing the character to readers.

That's the first page of it above. As you can see, the story is being told by a lawman, one Sheriff Chase of Oscaloosa County, Florida. He would serve as the narrator for this and all future Detective Chimp stories in the pages of Rex the Wonder Dog, and he would then return to do so in the "Whatever Happened to Rex the Wonder Dog?" strip from 1981's DC Comics Presents #35. 

On page two Bobo wanders on-panel, wearing a bright orange ball cap and crying "Ooo--Eee!", which we are told is "Bobo speak" for "You" and "Me." While Bobo proceeds to peel a banana, the sheriff relates the story of how he came to meet Bobo.

Animal trainer Fred Thorpe, of "the famed Thorpe animal farm", has called the sheriff out to visit him one afternoon. While there, the sheriff sees Bobo riding a bicycle with food in its basket. Bobo then begins measuring out the milk that he will feed to Tombo, the gorilla. Are there other animals on this famed animal farm besides the two primates? Perhaps, but these are the only two we see in this strip.

When the sheriff leaves, he says aloud to himself how strange it was that Thorpe had called him out there to tell him something important, but then just ended up talking about Bobo the whole time. Later at his office, the sheriff gets a call from Thorpe's niece, Alice: Thorpe has been shot and killed!

The only witness to the crime? Bobo! 

The chimpanzee seems all excited, and when he takes the sheriff by the hand and leads him back to his car, the sheriff thinks that Bobo must be trying to take him to the killer. Once in the car, Bobo points directions, and he ends up leading the sheriff back to the office he had just left from.

There's no one there but the sheriff's secretary, Pete Drummond, who laughs about it. 

"Those monks are dumb," Pete says while loading a revolver, "Always up to silly tricks!"  

It's outside the sheriff's office that Bobo gets his first line of dialogue in English. While he vocalizes "Ch-Chk!", a thought balloon tells us what he's really thinking: "If only they would listen to me-- But they won't!"

This is how Bobo will continue to communicate for the next 40 years or so, making chimpanzee noises out loud, and thinking in the English language, often in quite simple sentences. 

What Sheriff Chase and Alice failed to understand is that the reason Bobo had led the sheriff back to his own office is because that's where the killer was. Pete Drummond is the one who shot Thorpe. (This isn't that mysterious of a mystery, really, as Drummond is the only other character in the whole story. But then, it is only seven and a half pages long, so it's not like Broome had room to introduce any other suspects.)

Realizing Bobo can actually finger him, Drummond returns to the farm to silence the ape once and for all...with a bullet. Bobo is on to him though, and he escapes his cage and leads the killer on a chase through the nearby forest, where he continually frustrates him—pelting him with coconuts, leading him into quicksand, slapping him with a bent back branch—before the chase ends back at the farm. 

Seeing the sheriff had also arrived there, Drummond tells his boss that it was Bobo who had killed Thorpe...and that the ape had then tried to kill him, too. 

Bobo, meanwhile, opens Tombo's cage, and the much bigger, scarier ape grabs Drummond and forces a full confession from the killer.

In the very last panel, we see Alice handing Bobo a bunch of bananas from a crate marked "For Bobo, Sheriff Chase", as she tells him the sheriff plans to send him such a crate every month for the rest of his life.

"Ch-- Ch--" Bobo says, while thinking, "Boy oh boy!" 

It sure reads like it's meant to be a one-off story, and that Bobo had returned to the Thorpe farm to live out his days with Alice, enjoying crate after crate of bananas. 

But someone must have wanted more Detective Chimp stories, be it DC Comics, or Broome and Infantino, or Rex the Wonder Dog readers. 

Because while the sheriff and Bobo took Rex #5 off (according to the Grand Comics Database, that issue's non-Rex story was "The Saga of Leapin' Lena," starring a kangaroo), they returned in issue #6, and a Detective Chimp story ran in all 40 of the remaining issues of the series.

That second Detective Chimp story in Rex #6 was entitled, appropriately enough, "The Return of Detective Chimp!" 

In it, Bobo dons his Sherlock Holmes-style deerstalker cap for the first time, the sheriff saying he had bought it for him. He also starts referring to Bobo as his assistant...perhaps Bobo took Drummond's job...?

Once again, there's a murder with relatively few suspects, and while the sheriff investigates, it's Bobo who ultimately solves the crime. 

This would be the basic pattern of all the Detective Chimp shorts from the pages of Rex. If you would like to read them for yourself, DC collected them all in 2023's The Detective Chimp Casebook (which also includes the DC Comics Presents back-up in which Bobo and Rex team-up, and takes its cover from 2007's Helmet of Fate: Detective Chimp #1, the only other comic in which Bobo's name is in the title).