Drawing on ideas from Discourse Grammar (Heine et al. 2013), this article examines characteristics of the Japanese reduplicated mimetics, arguing that they are transcategorial, able to function across different planes of grammar, either as mimetic adverbs belonging to Sentence Grammar (SG) or mimetic “theticals” belonging to Thetical Grammar (TG) (Kaltenböck et al. 2011: 879). The former expresses a manner of an action, typically occurring in the immediately preverbal position, as in huwahuwa (to) uku [mim quot float] ‘float lightly ’. By contrast the latter is the speaker’s re-enactment of the event, as in the case of “ Huwahuwa, shita de tsubuseru toohu gurai no katasa desu.” ‘Fluffy-fluffy, (the baby food should) have softness like tofu that can be crushed by (your) tongue.’, where the mimetic ‘re-enacts’ the speaker’s mouth feel (fluffiness) when she put the food into her mouth. The particle drop of the reduplicated mimetics is syntactically optional in SG, but obligatory in TG. The article suggests adding mimetics to the list of theticals, as the fronted zero-marked mimetics followed by a pause display three of the defining prototypical properties of theticals (Kaltenböck et al. 2011): (i) prosodic property (they display comma intonation), (ii) syntactic independence (they are not modifiers of the predicate), and (iii) semantic non-restrictiveness (they do not restrict the semantic content of the predicate).