Extraplanar Probe is a 2/2 Construct creature as long as it has a counter on it. It's still an artifact.

{U}: Put a vigilance counter on Extraplanar Probe.

{U}{U}: Put a flying counter on Extraplanar Probe. Activate only if Extraplanar Probe has vigilance.

{U}{U}{U}: Put a +1/+1 counter on Extraplanar Probe. Activate only if Extraplanar Probe has flying.