Given the following context:

Stereolab introduced easy-listening elements into their sound with the EP Space Age Bachelor Pad Music, released in March 1993. The work raised the band's profile and landed them a major-label American record deal with Elektra Records. Their first album under Elektra, Transient Random-Noise Bursts with Announcements (August 1993), was an underground success in both the US and the UK. Mark Jenkins commented in Washington Post that with the album, Stereolab "continues the glorious drones of [their] indie work, giving celestial sweep to [their] garage-rock organ pumping and rhythm-guitar strumming". In the UK, the album was released on Duophonic Ultra High Frequency Disks, which is responsible for domestic releases of Stereolab's major albums.In January 1994, Stereolab achieved their first chart entry when the 1993 EP Jenny Ondioline, entered at number 75 on the UK Singles Chart. (Over the next three years, four more releases by the band would appear on this chart, ending with the EP Miss Modular in 1997.) Their third album, Mars Audiac Quintet, was released in August 1994. The album contains the single "Ping Pong", which gained press coverage for its allegedly explicit Marxist lyrics. The band focused more on pop and less on rock, resulting in what AllMusic described as "what may be the group's most accessible, tightly-written album". It was the last album to feature O'Hagan as a full-time member. He would continue to make guest appearances on later releases. The group issued an EP titled Music for the Amorphous Body Study Center in April 1995. The EP was their musical contribution to an interactive art exhibit put on in collaboration with New York City artist Charles Long. Their second compilation of rarities, titled Refried Ectoplasm (Switched On, Vol. 2), was released in July 1995.

answer the following question:

What is the last name of the person who would continue to make guest appearances on later releases? 

O'Hagan