Smeargle's a Gen 2 pokemon, which is some of the problem there >.> That said, elf's set is definitely from Gen 3, forget if it's in the topic. I know a very similar topic is in the redone Gen 4 topic (which isn't the one linked in the archive! If tal/dhyer wanna fix that).
Probably my fault, I said most of the pokemon were gen 1, which is true, Smeargle's just an exception.
It's not really an arbitrary set, mind. Smeargle's a Normal type, so he wants Normal moves for the STAB. The stats are abysmal (.5 or so on both durabilities? Half average or so on offensive stats? yeah), so non-STAB moves are only good if you can guarantee a weakness. Given the bad durability, a standard slugfest is a bad idea, so banking on Sleep hype is the way to go. Pokemon sleep lasts 2-5 turns, so he has a limited time to kill the opponent. Hyperbeam is the strongest non-suicidal normal move (150 base power, 225 after STAB), but you lose your next turn after using it. Due to Smeargle stats, this is nowhere near fatal. Belly Drum is the fastest way to boost your Attack stat (instant +6 modifier, or 3x base damage) and the downside doesn't matter as long as the opponent is still asleep. If the opponent is more durable than average, then lowering their defense (you can't boost a stat more than +6, even if you could belly drum twice in a row) is the only way to go, and Screech is the fastest way to do that (-2 modifier. I forget what this does precisely, I think 66% added damage?).
In summary, Sleep is the best stat to use, because it's debilitating, has a 100% accurate version (Spore), and Smeargle needs to debilitate the opponent. Belly Drum and Screech are the most effective stat modifiers available as long as you aren't being attacked, and Smeargle's peak damage is with Hyperbeam (in Gen 2/3. In Gen 4, Hyperbeam is a special attack, and while Smeargle's special is no worse than his attack, there's no +6 Special buff. However! There's a new move, Giga Impact, which is exactly the same as Hyperbeam except it's physical, ie identical to gen 1-3 Hyperbeam. So gen 4 just replaces Hyperbeam with Giga Impact and is effectively identical in performance). So yeah, for DL purposes where you're not guaranteed to hit a weakness, you can't set up for your teammates, can't bait-and-switch foes, and so forth, it's Smeargle's best set for a one on one battle and there's not... really anything else worth messing with, despite the option of EVERYTHING EVER. Funny really.
Edit: trivia! I dunno about the DL proper, but I always tag all pokemon as 'Pokémon' because I'm comfortable voting on them in whatever form is most current, whether they technically are catchable in that version or not, and don't want to discourage others who vote similarly. Additionally, given all the remakes and so forth, a randomly selected pokemon has about a 75% chance of being "Pokémon Series" anyway. 'sides, having to write 'Pokémon Gold/Silver/Crystal' or similar next to everything would get tiresome and looks ugly >.>
