… the 2nd Doctor, played by Patrick Troughton.
Comparing Eleven to Two is practically a cliche at this point, but, hey, it fits. Matt Smith himself has said in interviews that Troughton inspires a great deal of his performance. (And costume - Smith suggested the bowtie as an ever-cool tribute.)
They’re certainly both silly - Smith’s is the face that spawned a thousand gifs, while Troughton’s approach to filming can be partly summarized as “improvising nonsense and getting away with it because there wasn’t enough time to do re-takes.” But they’re also incredible at serious moments. Two doesn’t come with nearly as much heartbreaking continuity, but Troughton still pulls off scary, sweet, and somber scenes that hold up after half a century.
If you’re going to start watching Two, might as well watch the story that Matt Smith did: Tomb of the Cybermen. It’s got some flaws (including a racially uncomfortable side character - thanks, 1960s!) but has a solid mix of humor and suspense, and it’s a good showcase for companions Jamie and Victoria.