Babe

Mr. 4 is the male partner of Miss Merry Christmas.

Appearance
Mr. 4 is rather tall and fat, wearing a green shirt that covers most of his body with black pants and gray running shoes. Like all other officer agents, his number is expressed somewhere on his clothing or his person. Mr. 4 has an obscure "4" design on his shirt, as well as a "4" on his baseball bat.

Strangely, even though he is drawn with blond hair on the cover of volume 21 and in the anime, the manga itself depicts his hair color as black. This is not the first time though Oda has depicted a blond haired character this way; Yasopp is also shown with black hair in the manga even though he has blond hair.

Personality
Mr. 4 was the slow and dimwitted partner of Ms. Merry Christmas. He seems incapable of thinking for himself at all and often just does as his partner tells him to do. He laughs freely, but speaks rarely — in contrast to his partner, he speaks very slowly, usually taking most of a scene to articulate a short sentence.

Abilities and Powers
He is one of two officer agents without a Devil Fruit ability, the other being Miss Goldenweek. He is very strong, able to wield a baseball bat that weighs 4 tons with no effort. However, he is also extremely slow in nature, so without Miss Merry Christmas handling the 'intelligence', he would not succeed. He and his partner are actually, in terms of physical power, stronger than the Mr. 3 Team, as said by Crocodile, but are a lower rank because Mr. 3 is much smarter and tactical.

Lassou
Mr. 4 has a dog called Lassou, which was originally a gun, but "ate" the Inu Inu no Mi, Model Dachshund, a Devil Fruit, and became a gun-dog, who shoots exploding baseballs, even when he sneezes (when he's first introduced, he has a cold). Mr. 4 then takes out his 4 ton baseball bat and hits the balls at his enemies.

Techniques

 * Yonhyappon Punk Knock (四百本 猛打ノック, 400 Punk Knock): This attack's not officially named by him, but by his partner Ms. Merry Christmas. He has Lassou shoot a huge group of his exploding baseballs then Mr. 4 hits them back at a surprisingly swift speed into the cluster detonating them all at once and creating a massive explosion. This attack is called 400 Base Hits in the Viz Manga and 400 Base Knock in the 4Kids and FUNimation dubs.
 * Mogurazuka Yonban Kōsaten (モグラ塚 4番交差点, Molehill Intersection Number 4): A combo attack with Ms. Merry Christmas; first Ms. Merry Christmas uses her Mogurazuka Highway technique and carries the opponent past Mr. 4 who, upon hearing her call out the attack, smacks the captive with his 4-ton bat causing massive damage to anyone unlucky enough to be the victim of this attack, though he may accidentally hit an ally as he is too dim witted to note differences in the voice. This is called Moletown Cleanup Hitter in the Viz Manga and the FUNimation dub of movie 8, Woodchuck Batter Blaster in the 4Kids dub, and Molehill Intersection #4 in the FUNimation dub.

Arabasta
He, Lassou and Ms. Merry Christmas took on Usopp and Tony Tony Chopper during the Straw Hat Pirates' final fights with Baroque Works during the Arabasta arc. He managed to severely injure Usopp using a combined attack with Ms. Merry Christmas. But Usopp tricked him into knocking out his partner. Usopp then, using Chopper's horns as a slingshot, defeated Mr. 4 by shooting an extremely fast hammer at him (the move called Hissatsu UsoCho Hammer Suisei or 'UsoCho Hammer Comet), knocking him (and Lassou) into a stone structure. Mr. 4 and Ms. Merry Christmas were then blown up by one of Lassou's exploding baseballs.

Miss Goldenweek's "Operation: Meet Baroque Works"
All three were later seen in prison in Miss Goldenweek's chapter title mini-story. They managed to escape and are now working in the new Spiders Cafe. He is now the only male officer agent other than Mr. 5 to be working there.

Major Battles

 * Mr.4, Lassou and Miss Merry Christmas vs. Usopp and Tony Tony Chopper

Trivia

 * Miss Goldenweek's Colors Trap reveals that his dream was to become a pizza delivery boy, which is ironic since pizza delivery boys are known to be fast with their delieveries. ("Pizza within 30 hours" as his apron says, the saying usually used is minutes).
 * The Mr. 4 pair's theme is baseball. It is a reference to a baseball strategy where you have your best hitter as the 4th batter in the batting line-up. If the first 3 batters manage to get a base each, the 4th player then has a chance to get the best points for the team.
 * Mr. 4 is the high ranking sole male Baroque Works agent who does not have a Devil Fruit, his dog does though.
 * Some fans asked how Mr. 4 would sound talking under the effects of Foxy the Silver Fox's Noro Noro no Mi, seeing that he already talks slowly. Oda (as "Mr. 4") wrote exactly what would happen as a response but the example was short as there wasn't enough room on the page to post the full response.