Tux ‘n Tails (a.k.a. Coat ‘n Tails) appears to be a party pony, judging by the backcard story given on My Little Wiki.

Tux ‘n Tails is so excited! He’s having a party and you’re invited! Today is the birthday of two baby ponies, and Tux ‘n Tails is planning a surprise party for them. It’s almost time for the party, so help Tux ‘n Tails put on his bow tie to make him look as handsome as can be for this special event. This fun-loving pony is not available in any store, so order now and catch the excitement!