The phrase "surprise appearance" means showing up unexpectedly or without prior notice.
Sentences with «surprise appearance»
One of the biggest surprise appearances at E3 2014 was Uncharted 4. (techradar.com)
No wonder he makes so many surprise appearances in my life. (discovermagazine.com)
Our test car topped # 120,000 and there a few surprising appearances on the options list, not least floor mats (# 121) and a rear wiper (# 235). (evo.co.uk)