His early performance works, such as Gymnastics and Schizophrenia and 5teen3sy: Kicking Games of Lip, were antic and unpredictable, and characterized by dense language play, song and movement fragments and rapid transformations of character.

In the mid 1990s, Portnoy regularly performed in venues such as Surf Reality and Luna Lounge's weekly show "Eating It", the epicenter of New York's alternative comedy scene.

Instead, halfway through the performance, Portnoy ripped off his shirt, ran next to Dylan, and started dancing and contorting with the two-word poem "Soy Bomb" written across his chest.

Portnoy's long-standing investigation of social exchange, and the rules of communication and play, has been conducted through a series of 'abstract gambling' tables for Casino Ilinx (2008) and Filzzungeungewiss (2009); and conversation or inventional games drawing on 17th century universal or taxonomic languages for Fran Spafa Feda (2010); and the game-show format of 27 Gnosis (2012).

Central to many of Portnoy's projects is his tongue-in-cheek concept of 'Relational Stalinism', a form of relational aesthetics that works against "the fashionable promise that an artwork might offer a democratic magic, transforming inter-relational codes into something nicer…"[7] Unlike other artists who produce participatory artworks, Portnoy undermines the creation of a harmonious community by setting as many limitations as possible on the participants and then introducing destabilizing mechanisms, such as changing the rules in the middle of the game.

In carrot jokes "incongruities are rarely resolved and just pile on top of each other … Since the ground or ‘script’ is always shifting, the listener keeps trying to determine whether there is an overall story that could explain what the hell is going on".