For some reason, I could see that being another F2P thing where you start with objects from SMB1/SMB2J (Goombas, Koopas, original Bowser), but can get ones from SMB2U (Shy Guys, Birdo, Wart, vegetables), SMB3 (Boos, big enemies, suits, P switches, Koopalings, ground pounding Bowser), or SMW (Yoshi, spinny blocks with eyes, Koopa Clown Car) for a dollar or two each.