This is one of those cases where there are two hostas with the same name. One is registered and, therefore, the "official" version of H. 'Showtime' while the other is a non-registered plant and needs to be renamed to avoid further confusion.

This hybrid of H. 'Fragrant Bouquet' × H. 'Fragrant Candelabra' was registered cultivar by Paul Aden of New York in 1987. It grows into a large size hosta about 21 inches in height by 35 inches wide. The leaves are slightly shiny and slightly corrugated and wavy. White flowers are borne on 36 inch tall spikes in July.

According to The Hostapedia by Mark Zilis (2009), "Paul Aden registered 'Showtime' in 1987 and there is every indication that 'Abba Showtime' and 'Showtime' are the same plant...I have never seen it in a garden simply as 'Showtime'."

Hosta Helper will call this plant 'Showtime' (Aden)
 

Originated by Bob Balitewicz of Indiana, this non-registered cultivar is of unidentified parentage. It is a small size hosta with light yellow foliage. The ovate leaves are slightly wavy. 

Hosta Helper will call this plant 'Showtime' (Balitewicz)