Hobo Larry is a dirty, stray human that Malloy adopted as his pet. As you can tell by his name and appearance, he has no home to live in and he's a humiliating failure, a loser, having failed to find any purpose or value to society. He is the only known human that Malloy truly cares about until he was forced to put him down after Hobo Larry got bitten by a rabid hobo. Despite getting killed, he came back in Season 3 in "Steve the Fearless Pilot" and "Campin' Ain't Easy".
Hobo Larry is extremely disgusting, and his main characteristic trait is being utterly disgusting. He enjoys shitting in Woody's boots, eating his own shit for breakfast and having sex with a can of warm beans.
Hobo Larry calls himself "Hobo Larry" in third-person, he doesn't even use the pronouns "I" or "me". In "Write 'Em Cowboy" and Armoogeddon, Part 2, it is established that Hobo Larry lives in a dumpster behind Jorge's Stripper Daycare Center.