In 2015, due to being diagnosed with dystonia, Spinney no longer puppeteered Oscar full-time on the show. Eric Jacobson became Spinney's understudy for Oscar; sometimes lip-syncing to a prerecorded vocal track by Spinney, and other times doing the voice himself. Jacobson started voicing Oscar for new material in Season 48 after Spinney's semi-retirement. On October 17, 2018, Spinney announced his full retirement from the character beginning the very same week as he planned to finish his final recordings on the following day. His final performance as Oscar the Grouch (and Big Bird) aired the following year for the series' landmark 50th anniversary; however, his recorded lines were ultimately left unused.