This is my favorite fan theory, originally created by the Four Finger Discount people, I'm told, but I can't find it on their site:

In Simpsons episode 9F10, “Marge vs. the Monorail”, the town meeting is interrupted by a mysterious character named Mr. Snrub. It’s a strange scene, because we never actually find out who Snrub is, and he doesn’t show up again in the rest of the episode, or indeed, in the rest of the series. However, I think I might have figured out why: Mr. Snrub is actually Mr. Burns in disguise.

I know it sounds implausible, but here is my reasoning:

Notice that “Snrub” has the same number of letters as “Monty”, Mr. Burns’s first name. Coincidence? Maybe, but there’s more.

Notice how quick Smithers is to agree with Snrub. I think the writers added this line as a subtle hint to the audience that there is some connection between Snrub and Burns. It also explains why Smithers was so willing to help Snrub in his time of need; because Snrub reminds him of Burns in some deep, ineffable way. If you listen closely to Snrub’s voice, it sounds an awful lot like Harry Shearer. Harry Shearer does the voice of many characters on The Simpsons, including Reverend Lovejoy, Seymour Skinner, Ned Flanders, and… Mr Burns. This doesn’t tell use for sure that Snrub is Burns, but it does narrow down the possibilities considerably.

When Snrub stands up to speak, he mentions that he comes from “someplace far away”. The writers of The Simpsons have always said that they consider Springfield to be somewhat flexible in its reality. For example, in one episode, Moe’s Bar is a short walk from the Simpsons’ house, but in the movie, it’s right next to the church. It is quite possible that, for the purpose of this scene, the writers wanted Mr Burns’ home to be “far away” from the Town Hall.

Notice that, in the above scene, when everyone in the Town Hall starts to get angry, Snrub instinctively tents his fingers, not unlike Mr Burns’ signature gesture. Now, to be fair, we occasionally see this gesture done by other characters, such as Homer, Bart, and even Lisa. But, I mean, still.

I will admit that this theory has some flaws. For example:

If Snrub is Burns, how did he grow the moustache so quickly? We saw Burns earlier in the episode dumping nuclear waste in the park, and he didn’t have a moustache then. This could partly be explained by the fact that, strictly speaking, we don’t know how much time has passed between that scene and the scene in the Town Hall. Perhaps this was enough time for Burns to grow the moustache that would disguise him as Snrub?

We all know that Smithers is in love with Burns, and that Burns doesn’t return Smithers’ affection. So, why is Burns so quick to embrace Smithers and hang on to him as they escape the building?

Look at this comparison of Snrub and Burns. They look almost nothing alike. For one thing, notice that Snrub has an extra wrinkle under his left eye. His face also settles into an expression that is open and happy, in contrast with Mr Burns’ scowl. In addition, Snrub has a more prominent overbite, the three liver spots on his head are further apart. I haven’t even gotten started on the colours: Snrub wears a dark blue suit with a black tie, and has light blue hair. Burns, in contrast, wears a teal suit with a pink tie, and has gray hair.

If Burns really was at the Town Hall, then who was running the nuclear plant? The lights are on in the building, which clearly means that the power is working. Snrub’s suggestion is that the city give the two million dollars to the Nuclear Power Plant. Why would Mr. Burns do this, since Burns already knows that the power plant is where the money came from? This leaves us with the possibility that Snrub was just an innocent person who spoke at the town meeting without being fully informed about the background details (hence why everybody was so mad at him for being so ignorant and unprepared).

So, at the end of the day, it’s hard to say who Snrub really is. It’s even more difficult to say why he showed up in only that one scene, and why he never showed up again — perhaps he was a character the writers wanted to introduce to the show, but could never find a good enough story for.

Like many fan theories, it’s probably not true, and I’m probably over-analyzing it, but it’s sure fun to think about!