Players playing weird characters breaking the immersion of my group

I have an issue with two players in my very large gaming group that I would like some advice from people who have perhaps dealt with players like these. In terms of age and experience, we’re all between the ages of 18 to 21, and we’ve variously been playing the game for 2 to 10 years. This particular instance there were only 4 players, but our extended group is near 20.

To put it simply, they will only play weird characters that break the immersion for my self and the other players. An example being a recent pathfinder game where the party consisted of a human gunslinger, human fighter, elf wizard, and a flail snail. It was a one of these things is not like the others situation. No one could really get into the game because of having to imagine this fairly typical group, plus a snail.

There was one instance where one of the players demanded to play an aquatic elf in a land locked campaign. It slowed the group down mechanically when they had to keep finding water. Another example is when the GM was adamant that the campaign he was running was human only, the player still went on to nag the GM to let him play anything from various pixies, plants, and even a swarm. The arguing wound up delaying the campaign from starting for several hours.

I’ve asked the players why they play these types of characters and they say things along the lines of:

  • Its too hard to play a humanoid character because there is too much to think about when playing a neurotypical standard humanoid
  • I want to play characters that no one can relate too
  • I like playing with self imposed restrictions in terms of how I act.

We have asked them as a group to play more normal characters and there have been mixed responses from the two. One will keep asking whoever is the DM until they break down and allow something. The other will play a more normal character but is clearly not having fun.

If anyone has had experience with a situation like this, how did you resolve it?